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Sciences 
Corporation 


23  WEST  MAIN  STREET 

WEBSTER,  N.Y.  14580 

(716)  872-4503 


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CIHM/ICMH 

Microfiche 

Series. 


CIHM/ICMH 
Collection  de 
microfiches. 


Canadian  Institute  for  Historical  Microreproductions  /  Institut  Canadian  de  microreproductions  historiques 


Technical  and  Bibliographic  Notes/Notes  techniques  et  bibliographiques 


The  Institute  has  attempted  to  obtain  the  best 
original  copy  available  for  filming.  Features  of  this 
copy  wdich  may  be  biblingraphically  unique, 
which  may  alter  any  of  the  images  in  the 
reproduction,  or  which  may  significantly  change 
the  usual  method  of  filming,  are  checked  below. 


D 


D 
D 


D 


D 


Coloured  covers/ 
Couverture  de  couleur 


I      I    Covers  damaged/ 


Couverture  endommagde 

Covers  restored  and/or  laminated/ 
Couverture  restaur6e  et/ou  pellicul6e 

Cover  title  missing/ 

Le  titre  de  couverture  manque 

Coloured  maps/ 

Cartes  g6ographiques  en  couleur 

Coloured  init  (i.e.  other  than  blue  or  black)/ 
Encre  de  couleur  (i.e.  autre  que  bleue  ou  noire) 


I      I    Coloured  plates  and/or  illustrations/ 


Planches  et/ou  illustrations  en  couleur 


Bound  with  other  material/ 
Rali6  avec  d'autres  documents 


Tight  binding  may  cause  shadows  or  distortion 
along  interior  margin/ 

La  reliure  serr^e  peut  causer  de  I'ombre  opj  de  la 
distortion  le  long  de  la  marge  intirieure 

Blank  leaves  added  during  restoration  may 
appear  within  the  text.  Whenever  possible,  these 
have  been  omitted  from  filming/ 
II  se  peut  que  certaines  pages  blanches  ajouties 
lors  d'une  restauration  apparaissent  dans  le  texte, 
mais,  lorsque  cela  Atait  possible,  ces  pages  n'ont 
pas  At6  filmies. 

Additional  comments:/ 
Commenfaires  suppl^mentaires: 


L'Institut  a  microfilm^  le  meilleur  exempiaire 
qu'il  lui  a  6t4  possible  de  se  procurer.  Les  details 
de  cat  exempiaire  qui  sont  peut-dtre  uniques  du 
point  da  vue  bibliographique,  qui  peuvent  modifier 
une  image  reproduite,  ou  qui  peuvent  exiger  itne 
modification  dans  )a  mdthode  normale  de  filmage 
sont  indiquis  ci-dessous. 


D 
D 

n 
0 

D 


D 


Coloured  pages/ 
Pages  de  couleur 

Page.''  damaged/ 
Pages  endommag^es 

Pages  restored  and/or  laminated/ 
Pages  rastaur^es  et/ou  pelliculies 

Pages  discoloured,  stained  or  foxed/ 
Pages  d6color6es,  tachetdes  ou  piqu6es 

Pages  detached/ 
Pages  d6tach6es 


r~~l    Showthrough/ 


Transparence 

Quality  of  print  varies/ 
Quality  in6gale  de  I'impression 

includes  supplementary  material/ 
Comprend  du  materiel  supplimentaire 

Only  edition  available/ 
Saule  Edition  disponible 


Pages  wholly  or  partially  obscured  by  errata 
slips,  tissues,  etc.,  have  been  refilmed  to 
ensure  the  best  possible  image/ 
Lea  pages  totalement  ou  partiellement 
obscurcies  par  un  feuillet  d'errata,  une  pelure, 
etc.,  ont  6t6  filmies  A  nouveau  de  fapon  d 
obtenir  la  meilleure  image  possible. 


This  item  is  filmed  at  the  reduction  ratio  checked  below/ 

Ce  document  e^^t  film6  au  taux  de  reduction  indiqui  ci-dessous 

10X                             14X                              18X                             22X 

26X 

30X 

; 

J 

12X 


16X 


20X 


24X 


28X 


32X 


The  copy  filmed  here  has  been  reproduced  thanks 
to  the  generosity  c;: 

Dana  Porter  Arts  Library 
University  of  Waterloo 


L'exemplaire  fiimd  fut  reproduit  grfice  d  la 
g6n6rosit6  de: 

Dana  Porter  Arts  Library 
University  of  Waterloo 


The  Images  appearing  here  are  the  best  quality 
possible  considering  the  condition  and  legibility 
of  the  original  copy  and  in  keeping  with  the 
filming  contract  specifications. 


Original  copies  in  printed  paper  covers  are  filmed 
beginning  with  the  front  cover  and  ending  on 
the  last  page  with  a  printed  or  illustrated  impres- 
sion, or  the  back  cover  when  appropriate.  All 
other  original  copies  are  filmed  beginning  on  the 
first  page  with  a  printed  or  illustrated  impres- 
sion, and  ending  on  the  last  page  with  a  printed 
or  illustrated  impression. 


The  last  recorded  frame  on  eich  microfiche 
shall  contain  the  symbol  —«»- (meaning  "CON- 
TINUED"), or  the  symbol  V  (meaning  "END"), 
whichever  applies. 


Les  images  suivantes  ont  6ti  reproduites  avec  le 
plus  grand  soin,  compte  tenu  de  la  condition  et 
de  la  nettet6  de  l'exemplaire  film6,  et  en 
conformity  avec  les  conditions  du  contrat  de 
filmage. 

Les  exemplaires  originaux  dont  la  couverture  en 
papier  est  imprimde  sont  filmds  en  commenpant 
par  le  premier  plat  et  en  terminant  soit  par  la 
dernidre  page  qui  comporte  une  empreinte 
d'impression  ou  d'illustration,  soit  par  le  second 
plat,  selon  le  cas.  Tous  les  autres  exemplaires 
originaux  sont  filmds  en  commenqant  par  la 
premidre  page  qui  comporte  une  empreinte 
d'impression  ou  d'illustration  et  en  terminant  par 
la  dernidre  page  qui  comporte  une  telle 
empreinte. 

Un  des  symboles  suivants  apparaitra  sur  la 
dernidre  image  de  cheque  microfiche,  selon  le 
cas:  le  symbole  —^  signifie  "A  SUIVRE",  le 
symbols  V  signifie  "FIN  ". 


Maps,  plates,  charts,  etc.,  may  be  filmed  at 
different  reduction  ratios.  Those  too  large  to  be 
entirely  included  in  one  exposure  are  filmed 
beginning  in  the  upper  left  hand  corner,  left  to 
right  and  top  to  bottom,  as  many  frames  as 
required.  The  following  diagrams  illustrate  the 
method: 


Les  cartes,  planches,  tableaux,  etc.,  peuvent  dtre 
film^s  d  des  taux  de  reduction  diffdrents. 
Lorsque  ie  document  est  trop  g   >nd  pour  dtre 
reproduit  en  un  seul  clichd,  il  e&   fiimd  d  partir 
de  Tangle  eupdrieur  gauche,  de  gauche  d  droite, 
et  de  haut  en  bas,  en  prenant  le  nombre 
d'images  n6cessaire.  Les  diagrammes  suivants 
illustrent  la  m6thode. 


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2 

3 

1 

2 

3 

4 

5 

6 

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TEXT    BOOK 


OF 


PHYSIOLOGY 


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TEXT   BOOK 


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PHYSIOLOGY, 


BY 


J.  FULTON,  M.D.,  M.R.C.S.,  Eng.;  L.R.C.P.,  Lon. 

TROKKSSOR  OP  PIIYHIOtiOQY  AND  bANITARY  SCIBNCE  IN  TRINITY  MKDICAL 

COLLEGK,  TORONTO  ;  8UR0E0N  TO  THE  TOROSTO  OKNKRAli 

HOHl'ITAL,    AND   PHYSICIAN   TO  THE   IIO.MK 

KOR  INCl'RABLKS,  TORONTO. 


t  i 


SECOND  EDITION,  REVISED  AND  ENLARGED, 
WITH  NUMEROUS  ILLUSTRATIONS. 


"labor  omnia  vincit.  ' 


I'lIILAUELrillA: 
LINDSAY   &    BLAKISTON 

TORONTO : 

WILLING    &    WILLIAMSON 


1879. 


Property  of  the  Library 
University  of  Waterloo- 


Entered  according  to  Act  of  the  Parliament  of  Canada,  in  the  Year  One  Thousand  Eight 
Hiinilred  and  Seventy-nine,  by  J.  FrLTON,  M.D.,  in  the  Office  of  the  Mi:iisterof  Agri- 
cultinu,  at  Ottawa,  D.C. 


Entered  according  to  Act  of  Congress,  in  the  Year  One  Tliousand  Eight  Hundred  and 
Seventy-nine,  by  A.  L.  Eti/roN,  M.D.,  in  the  Office  of  tlie  Librarian  of  Congress,  at 
Washington,  D.C. 


Dudley  &  Birxs,  Printers, 

11  Colhornc  Street,  Toronto. 


PREFACE  TO  THE  SECOND  EDITION, 


The  science  of  Physiology  has  been  so  much  advanced 
in  almost  every  department  of  the  subject,  since  the  issue 
of  the  first  edition,  that  the  preparation  of  the  present  one 
has  been  no  easy  matter.  The  very  favorable  reception, 
however,  which  was  accorded  the  first  edition,  has  induced 
me  willingly  to  undertake  the  self-imposed  task.  Many  of 
the  chapters  have  been  re-written,  and  much  new  matter 
added  ;  but  while  every  part  has  received  careful  revision, 
the  original  plan  of  arrangement  has  been  rigidly  adhered 
to,  as  that  best  adapted  to  the  wants  of  those  for  whom 
it  Wivs  written. 

My  experience  as  a  teacher  in  the  department  of 
Physiology  during  the  last  fifteen  years,  formerly  in 
Victoria  Medical  College,  and  latterly  in  the  University 
of  Trinity  College,  has  led  me  to  the  conclusion  that 
Physiology  can  be  best  taught  in  connection  with  Histo- 
logy, and  with  this  view  I  have  endeavored  to  supply  a 
prevailing  want  in  the  ordinary  text  books,  by  the  intro- 
duction of  a  concise  history  of  this  interesting  subject. 
It  has  been  truly  said  that  a  knowledge  of  Anatomy  is 
the  keystone  to  Medicine,  and  it  is  equally  true  that  a 
knowledge  of  Histology  is  the  keystone  to  Physiology. 

Illustrations  have  been  introduced  wherever  they  ap- 
peared desirable,  and  in  order  to  prevent  the  volume  from 
being  too  expensive,  such  illustrations  as  did  not  appear 
necessary  to  the  elucidation  of  the  text  have  been  omitted. 


j 


VI. 


The  illustrations  are  partly  new  and  partly  borrowed  from 
recognized  authorities,  and  special  acknowledgment  must 
be  made  of  those  obtained  from  jAMES  CAMPBELL,  Pub- 
lisher, Boston,  U.S.  It  was  not  considered  desirable,  as  a 
rule,  in  a  work  of  this  kind,  to  quote  authorities  for  the 
statements  in  the  text,  as  it  would  have  required  numerous 
references  to  home  and  foreign  books  and  periodical  litera- 
ture, which  would  have  been  not  only  useless,  but  confusing 
to  the  generality  of  readers. 

Notwithstanding  the  number  of  most  excellent  works 
on  Physiology  published,  a  well  digested  te  :t  book  on  this 
subject,  adapted  to  the  wants  of  the  advanced  medical 
student  and  the  general  practitioner,  is  still  a  desideratum 
in  medical  literature.  This  work  is  chiefly  intended  for 
medical  students,  but  it  is  hoped  that  it  may  also  prove 
serviceable  to  medical  practitioners,  more  especially  those 
who  have  students  under  their  instruction. 


J.  FULTON. 


£i.oi.N  PiiACK,  .'iiK!  Cliiuvli  St.,  Toronto. 


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CONTENTS. 


PAGE 

INERODUCTION    II 

CHAPTER  I. 

Proximate  Principles 14 

Definition  of  a  Proximate  Principle 14 

Classification  of  Proximate  Principles IS 

Proximate  Principles  of  the  First  Class 16 

Water 16 

Sodium  Chloride 17 

Potassium  Chloride ...  18 

Lime  Phosphate 19 

Lime  Carbonate 19 

Sodium  and  Potassium  Carbonates 20 

Sodium  and  Potassium  Sulphates 20 

Magnesium  Phosphate  and  Carbonate 21 

Gases 22 

Proximate  Principles  of  the  Second  Class 22 

Starch 23 

Glycogen 25 

Sugars 26 

Oils  and  Fats 29 

Proximate  Principles  of  the  Third  Class 33 

Albumen 35 

Albuminose  or  Peptone 37 

Fibrin   38 

Casein 40 

Globuline 41 

Pepsine , , .  41 

Pancreatine 42 

Ptyaline 42 

Mucosine 42 

Musculine 42 

Cartilagine 42 

Collagen 43 

Elasticine 43 

Keratine   43 

Coloring  Matters 43 

Hemoglobine 43 

Melanine 44 

Bilirubine  and  Biliverdine 44 

Urosacine  or  Urochrome 45 

Luteine 45 

€rvstallizable  Nitrogenous  Mattees 45 

Lecithine 45 

Cerebine 46 

Leucine 47 


I 


Vlll. 


CHAPTER  II. 

I'AOE 

Elementary  or  Primary  Forms  ok  Tissue 46 

Protoplasm 47 

Cells,  shape,  size  and  structure 47 

Cytogenesis 5' 

Conditions  necessary  to  Cell  growth 53 

Permanent  Change  in  the  Shape  of  Cells. . S3 

Temporary  Change  in  the  Shape  of  Cells 54 

Cause  of  Organization 55 

Function  of  Cells  56 

Manifestations  of  Cell  Life 57 

Granules 57 

Simple  Fibres 57 

Simple  Membranes 58 

CHAPTER    HI. 

Tissues 60 

White  Fibrous  or  Connective  Tissue 60 

Yellow  Fibrous  or  Elastic  Tissue 62 

Areolar  Tissue 64 

Adipose  Tissue 65 

Cartilage 66 

Gelatinous  and  Reticular  Tissue 71 

Bone 72 

Teeth 79 

Muscle 83 

CHAPTER   IV. 

Membranous  Expansions 96 

Epithelium 97 

Serous  Membranes loi 

Synovial  Membranes 102 

Mucous  Membranes 103 

Appendages  of  the  Mucous  Membrane 105 

^             Integument 1 12 

Appendages  of  the  Integument 116 

CHAPTER   V. 

Digestion 125 

Prehension  1 32 

Mastication 132 

Insalivation 134 

Deglutition 137 

Chymification 1 39 

Chylification 144 

Defecation 156 

CHAPTER    VI. 

Absorption      158 

Villi  and  Lacteals 158 

Lymphatic  Vessels  and  Glands 159 

Mechanism  of  Absorption  162 

Absorption  by  the  Villi  and  Lacteals 165 

Absorption  by  the  Blood  Vessels 166 

Absorption  by  the  Lymphatics 167 

Glandulse  Solitariae ^, . .  167 


IX. 


CHAPTER   vir. 

TAOE 

Blood i68 

Physical  Character  of  the  IMood i68 

Microscopical  Appearance  of  tlie  Blood 169 

Chemical  and  Structural  Characters  of  the  Blood 176 

Difference  i)etween  Arterial  and  Venous  Blood 180 

Conditions  which  Influence  the  Ciiaracter  of  the  Blood 183 

Coagulation  and  Vital  Properties  of  the  Blood 188 

Circumstances  which  Promote  Coagulation 191 

Circumstances  which  Retard  Coagulation 192 

Function  of  the  Constituents  of  the  Blood 194 

Relation  of  the  Blood  to  the  Living  Organism 198 

CHAPTER    VIII. 

Circulation 200 

The  Heart  and  Circulation 200 

Proofs  of  the  Circulation   203 

Action  of  the  Heart 206 

Arteries  212 

Veins 219 

Capillaries 222 

Velocity  f.f  the  Circulation 225 

Fa'tal   Circulation 227 

CHAPTER    IX. 

KliSPIRATION 230 

The  Lungs 230 

Meclinnism  of  Respiration 233 

Influence  of  the  Nerves  in  Respiration 237 

Modification  of  the  Respiratory  Movements 238 

Changes  in  the  Respired  Air 239 

Changes  in  the  Blood  during  Respiration 242 

Elfects  of  the  Arrest  of  Respiration 243 

CHAPTER   X. 

Animal  Heat,  Light  and  Electricity 244 

Heal 244 

Theory  of  the  Production  of  Heat 245 

Regulation  of  the  Temperature  of  the  Body 247 

Light 248 

Electricity 248 

CHAPTER    XL 

Secreting  Glands  and  their  Skcretions 252 

The  Liver 252 

The  Kidney , 256 

Secretion  of  Urine 259 

The  Mammary  Glands   , 266 

Milk 267 

CHAPTER   XII. 

Ductless  or  Vascular  Glands 270 

The  Spleen 270 

The  Supra-renal  Capsules 273 

The  Thymus  Gland 274 

The  Thyroid  Gland 275 


X. 


CHAPTER    XIII. 

PACK 

The  Nervous  Systkm 276 

Structure  of  the  Nervous  System 28 1 

Ganglia  of  Nerves 284 

Chemical  Composition  of  Nerve  Tissue 284  ■ 

Origin  and  Termination  of  Nerves 286 

Function  of  Nerve  Fibres 289 

Develop'v.ent  of  Nerve  Tissue 292 

Function  of  the  Nervous  Centres 293 

Rellcx  Action 295 

Nerve  force 295 

The  Spinal  Cord 296 

Function  of  the  Spinal  Cord    299 

Encephalon S^S- 

y.  ;;lulla  Oblongata 303 

Pons  Varolii 3°^ 

Cerebellum 3°7  . 

Cerebrum 3'° 

The  Mind  and  its  relation  to  the  body 324 

Cranial  Nerves 329 

Sympathetic  Nervous  System 336 

CHAPTER   XIV. 

The  SPEC! Ai,  Senses 340' 

Smell 340 

Sight 343 

Phenomena  of  Vision 35 1 

Accommodation  of  the  Eye  to  Vision 352 

Defects  of  Vision 35^ 

Hearing 35^ 

The  Mechanism  of  Hearing 362 

Sense  of  Taste 3^4 

Sense  of  Touch 3^6 

CHAPTER   XV.    ■ 

The  Voice 37° 

Larynx 37° 

Compass  of  the  Voice 373 

Ventriloquism  and  Stammering 374 

CHAPTER   XVI. 

Reproduction 375 

Action  of  the  Male 377 

Action  of  the  Female 37^ 

Corpus  Luteum 3^0 

Action  of  the  Oviducts 3^1 

Development  of  the  Ovum 3^2 

Formation  of  the  Amnion  and  Allantois    386 

Formalism  of  the  Chorio'i 3^^ 

Preparation  of  the  Uterus  for  the  Ovum 389 

Formation  of  the  Placenta 39° 

Umbilical  Cord  and  Amniotic  Fluid 39' 

Parturition 392 

General  Development  of  the  Embryo 392 


HUMAN  PHYSIOLOGY. 


INTRODUCTION. 


Physiology,  from  <pv(Tig,  "  nature,"  and  \oyog,  a  descrip- 
tion," in  its  general  senile,  has  for  its  province  the  investi- 
gation of  the  active  phenomena  j^resented  by  organized 
bodies,  and  is  divided  into  two  parts,  viz : — Animal,  and 
Vegetable  Physiology  :  the  former  treats  of  the  laws  that 
control  the  Animal  Kingdom ;  the  latter  relates  to  those  of 
the  Vegetable  Kingdom.  Animal  Physiology  may  also  be 
ilivided  into  two  parts,  viz  :  Human  Physiology,  and  Com- 
parative Physiology,  or  the  Physiology  of  the  lower  animals. 

Human  Physiology  treats  of  the  vital  phenomena  of  the 
human  species,  and  is  of  much  more  practical  importance  to 
the  medical  student  than  the  Physiology  of  the  lower  ani- 
mals, on  account  of  its  relation  to  Pathology  and  Therapeu- 
tics. The  study  of  Physiology  requires  an  intimate  know- 
ledge of  Anatomy  and  Chemistry,  in  order  that  the  student 
may  be  able  to  comprehend  the  character  of  the  structure 
he  is  examining,  and  the  substances  of  which  it  is  composed. 

Animate  bodies,  in  contradistinction  to  inanimate,  are 
possessed  of  organs,  each  of  which  has  a  special  structure 
and  distinct  olhce  to  i)erform  in  the  living  organism.  This 
action  or  office  is  called  its  function,  for  example,  the  func- 
tion of  the  liver  is  to  secrete  bile,  the  salivary  glands  to 
.secrete  saliva,  &c.  The  functions  of  the  different  organs  are 
also  mutually  dependent  on  each  other.  The  aeration  of 
the  blood  by  the  lungs,  is  dependent  on  its  circulation  by 
the  heart  and  blood  vessels,  and  the  circulation  of  the  blood 


iiif! 


12 


INTRODUCTION. 


|i^; 


is  dependent  on  the  influence  of  the  nerves,  and  the  C')ntinu- 
ance  of  life  is  the  result  of  the  continued  normal  and  har- 
monious action  of  all  the  organs  of  the  body. 

The  different  organs  of  the  body  are  sometimes  called 
systems,  as  the  osseous  system  ;  muscular  system  ;  nervous 
system  ;  arterial  system,  etc.  Each  organ  is  made  up  of 
smaller  parts  or  ultimate  elements,  which  can  only  be  seen 
and  studied  by  the  aid  of  the  microscope  ;  these  are  called 
the  "  anatomical,"  "  histological,"  or  "  microscopical  ele- 
ments ;  for  example,  the  primitive  fibrilke  are  the  ultimate 
or  "  anatomical  "  elements  of  muscular  tissue,  the  axis  cylin- 
der and  white  substance  of  Schwann  are  the  anatomical  ele- 
ments of  nerve  fibres,  etc. 

All  living  beings  pass  through  the  various  stages  of  birth,, 
growth,  development,  maturity,  and  decay.  These  are  the 
so-called  essentials  of  life.  Birth  means  the  separation  from 
the  parent,  with  power  of  independent  life  and  existence, 
inherited  fi'om  the  parent.  Growth  is  the  power  of  increas- 
ing in  size,  but  this  is  not  limited  to  living  beings.  A  stone 
or  a  crystal  may  also  grow,  but  it  is  by  the  laying  on  of 
particles  on  the  outside,  or  sv/perjicial,  while  the  growth  of 
living  organisms  {winter stitial,&n^  has  definite  limits.  Living^ 
organisms  absorb  the  material  required  in  growth  into  their 
interior,  and  assimilate  it  into  their  own  composition.  De- 
velopment indicates  the  successive  changes  through  which 
all  living  organs  must  pass,  before  they  are  capable  of  pro- 
perly ))erforming  their  functions.  The  brain  of  the  adult 
idiot  has  grown,  but  it  is  incapable  of  the  proper  perform- 
ance of  its  function,  from  want  of  proper  development. 
Maturity  is  the  attainment  of  complete  growth,  and  is  soon 
followed  by  decay  or  decline.  In  fact,  decay  may  be  said  to 
be  constantly  taking  place  in  our  bodies,  and  life  consists  in 
making  up  for  the  loss  attendant  on  it,  by  continual  repair. 
The  particles  of  our  bodies  die,  and  are  replaced  by  new  ones 
from  day  to  day,  although  the  individual  remains  the  same, 
so  that  it  may  be  said  of  our  bodies  "  in  the  midst  of  life 
we  are  in  death." 


INTRODUCTION, 


13 


Some  have  endeavoured  to  draw  a  distinction  between 
the  animal  and  vegetable  kingdoms,  but  while  this  is  a  mat- 
ter very  easy  of  accomplishment  in  the  higher  orders,  it  is 
very  difficult  to  say  where  vegetable  life  terminates  and 
animal  life  begins,  lower  in  the  scale.  The  distinction  whicli 
is  probably  the  most  reliable,  is  the  power  of  vegetables  to 
live  on  inorganic  matter,  as  water,  carbonic  acid,  and  am- 
monia, while  animals  cannot  subsist  without  organic  mate- 
rial. The  distinctions  sometimes  given,  bafiedon  the  difference 
in  chemical  composition — the  presence  or  absence  of  nitro- 
gen ;  the  power,  or  absence  of  movement,  and  the  presence 
or  absence  of  a  stomach  in  animals  and  vegetables  respec- 
tively, while  of  value  so  far  as  the  higher  orders  are  con- 
cerned, are  valueless  as  a  means  of  distinguishing  between 
the  two  classes,  low  down  in  the  scale  of  life. 


1 
I 


I  ! 


I 


14 


PROXIMATE  PRINCIPLES. 


CHAPTER  I. 


PROXIMATE  PRINCIPLES. 

Animal  bodies  are  composed  of  solids  and  fluids  :  the 
former  eribrace  the  various  textures  and  viscera  ;  the  latter 
the  blood,  chyle,  lymph  and  glandular  secretions.  The  same 
substance  may  be  fluid  in  one  part  of  the  body  and  solid  in 
another ;  for  example,  lime  phosphate  is  in  solution  in 
the  albumen  of  the  blood,  but  is  solid  in  the  bones.  Every 
animal  tissue  a:nd  fluid  contains  a  number  of  proximate 
principles  mingled  together  in  various  proportions. 

A  proximate  principle  may  be  defined  to  be  any  chemi- 
cal substance,  which  exists  in  the  animal  solids  or  fluids  in 
its  own  form,  and  which  may  be  extracted  in  an  unaltered 
state  by  chemical  process. 

But  it  must  not  be  supposed  that  every  substance  which 
can  be  extracted  from  an  organized  solid  or  fluid  by  chemi- 
cal neans  is  p  proximate  principle;  for  example,  sodium 
chlor.  1o  is  a  proximate  principle;  but  chlorine  is  not,  because 
it  does  't  exist  in  its  elementary  form  in  the  body.  Lime 
phosphate  is  a  proximate  principle  of  bone  ;  but  phos- 
phoric acid  is  not,  because  it  does  not  exist  in  a  free  state 
in  the  bony  tissue ;  still  less  phosphorus,  which  is  obtained 
only  by  the  decomposition  of  phosphoric  acid.  Again, 
fibrous  tissue,  when  boiled  steadily  for  thirty-six  or  forty 
hours,  yields  a  substance  called  gelatine ;  but  this  is  not  a 
proximate  principle,  since  it  does  not  exist  as  such  in  the 
body  but  is  produced  only  by  long-continued  boiling. 

In  extracting  the  proximate  principles  from  the  animal 
body,  only  the  simplest  chemical  means  should  be  employed. 
First,  evaporate  the  substance,  to  extract  and  estimate  the 


amou 
100° 
of  the 
water 

Col 
alcoh( 


inff 


PROXIMATE  PRINCIPLES. 


15 


amount  of  water.  The  temperature  should  not  be  above 
100°  (21 2"^)  because  a  higher  degree  would  change  some 
of  the  animal  ingredients.  Then  dissolve  out  the  salts  with 
water. 

Coloring  matter,  or  pigments,  may  be  detracted  by 
alcohol ;  oils  and  fats  by  ether.  Some  of  the  salts  may  be 
removed  by  double  decomposition.  Thus,  sodium  glyko- 
cholate  or  tauro-cholate  may  be  precipitated  by  lead  ace- 
tate, forming  lead  glyko-cholate  or  tauro-cholate  which 
may,  in  its  turn,  be  decomposed  by  sodium  carbonate  form- 
ing the  original  sodium  glyko-cholate  or  tauro-cholate. 
Sometimes  a  proximate  principle  cannot  be  separated  in  au 
entirely  unaltered  state.  Albumen  requires  to  be  coagulated 
by  heat  or  nitric  acid  ;  the  fibrin  of  the  blood  can  only  be 
separated  by  coagulation,  which  it  does  spontaneously ; 
hence  they  lose  their  original  character  of  fluidity,  and  are 
permanently  altered. 

The  proximate  principles  are  divided  into  five  classes : 

1st.  Crystallizable  substances  of  inorganic  origin,  as 
water,  sodium  chloride,  lime  carbonate  and  phosphate, 
etc.  They  are  derived  mostly  from  exterior  sources.  They 
are  found  in  organized  as  well  as  in  unorganized  bodies, 
and  have  a  definite  chemical  composition. 

(In  this  class  may  also  be  included  the  gases,  as  oxygen, 
hydrogen,  nitrogen,  carbonic  acid,  carburetted  and  sulphur- 
etted hydrogen). 

2nd.  Crystallizable  substances  of  organic  origin,  or  non- 
nitrogenized  substances,  as  starch,  sugars,  oils,  and  fats. 
They  are  found  only  in  organized  bodies,  are  crystallizable 
(excepting  starch),  and  have  a  definite  chemical  composition. 
They  contain  carbon  in  large  proportion  but  no  nitrogen. 

3rd.  Organic  substances  propei',  "nitrogenized  substances," 
"  albuminoid  substances,"  or  "  protein  compounds,"  as  albu- 
men, fibrin,  casein,  «Sz;c.  They  difi[er  from  the  two  former 
classes  in  the  fiict  that  they  contain  nitrogen.  They  are 
exclusively  organic  in  their  origin,  are  not  crystallizable, 
and  are  not  definite  in  their  chemical  composition. 


c 
c 

» 

c 


i: 
« 


t 
I 

V 


N 


w 


16 


PROXIMATE  PRINCIPLES. 


4th.  Coloring  matters,  as  hemoglobine,  melanine,  biliru- 
bine,  biliverdine,  etc. 

5th.  Crystallizable  nitrogenous  substances,  as  urea,  crea- 
tine creatinine,  lecithine,  cerebrine,  etc. 

PROXIMATE  PRINCIPLES   OF  THE  FIRST  CLASS. 

Water,  H^O. — Water  is  the  most  important  of  the  in- 
organic principles,  and  is  found  in  all  parts  of  the  body. 
In  the  solids  it  does  not  exist  in  a  fluid  state,  but  is  incor- 
porated with  the  substance  of  the  tissue.  It  maj'  be  called 
"  xvaUv  c,  cortiposition,"  in  contradistinction  to  what  is 
called  in  chemistry  "  water  of  crystallization"  It  con- 
stitutes about  two-thirds  of  the  entire  weight  of  the  body. 

The  following  table  shows  the  proportion  of  water  per 
1,000  parts  in  different  solids  and  fluids  : — 

quantity   of   water    in   1,000   PARTS. 


■a 


Enamel  of  the  Teeth.. . .     2 

Epidermis 2>7 

Teeth loo 

Bones 130 

Tendons 500 

Cartilage 550 

Muscles 750 

Ligaments 768 


!1 


^ 


Blood 795 

Bile 880 

Milk 887 

Pancreatic  Juice 900 

Urine 936 

Gastric  Juice 975 

Perspiration 986 

Saliva 995 


Origin  and  Discharge  of  Water. — It  is  introduced 
with  the  fluid  and  solid  elements  of  the  food.  It  is  also  be- 
lieved to  be  formed  in  the  body  from  the  union  of  oxygen  and 
hydrogen,  as  they  are  liberated  from  organic  combinations. 
The  amount  of  water  taken  into  the  system  by  an  adult,  in 
the  course  of  24  hours,  varies  from  3i  to  4  pounds.  It  is  dis- 
charged from  the  body  in  four  different  ways — by  the  urine, 
faeces,  perspiration,  and  breath — about  50  per  cent,  being  dis- 
charged by  the  urine  and  faeces,  30  per  cent,  by  the  per- 
spiration and  20  per  cent,  by  the  lungs.  These  proportions 
will  vary  according  to  circumstances ;  for  example,  in  warm 
weather,  when  the  skin  is  more  active,  and  the  perspiration 
more  abundant,  the  quantity  of  urine  is  diminished.     The 


PROXIMA  TE  PAVXC/PLES. 


17 


quantity  of  water  discharged  b}'  the  lungs  varies  also,  with 
the  state  of  the  atmosphere  and  the  pulmonary  circulation. 
The  water  is  not  discharged  pure,  but  is  mingled  with 
various  salts,  animal  matters,  and  odoriferous  subs-tances. 

Function.— It  holds  in  solution  different  salts  and  sub- 
stances of  excretion,  and  gives  fluidity  to , the  blood  and 
secretions.  It  is  a  most  important  article  of  diet,  and  is 
necessary  both  for  the  introduction  of  substances  into  the 
body,  and  their  elimination  from  it.  It  gives  to  cartilage 
its  elasticity,  and  to  tendons  their  toughness  and  pliability, 
for,  if  water  be  expelled  from  a  piece  of  cartilage  by 
evaporation,  it  becomes  dark  in  colour,  semi-transparent, 
hard  and  inelastic.  The  same  thing  is  true  of  musJes, 
tendons,  etc. 

Sodium  Chloride,  NaCl. —  Sodium  chloride  is  next  in 
importance,  and  is  found  in  all  parts  of  the  body  except  the 
enamel  of  the  teeth.  The  entire  quantity  in  the  body  has 
been  estimated  b}'  Dr.  Laukester,  at  one-quarter  of  a  pound, 
avoirdupois.  It  exists  in  the  greatest  quantity  in  the  fluids. 
In  blood,  for  example,  it  is  more  abundant  than  all  the  other 
salines  taken  together.  The  following  is  a  list  of  the 
quantities  in  the  most  important  solids  and  fluids.: — 

QUANTITY   OF   SODIUM   CHLORIDE    IN    1,000   PARTS. 


Muscles. 
Bones. . 
Milk.... 
Saliva. . 
Urine. .  . 
Bile.... 


■7 

•3 
.1.5 

5-5 
.^1 


Lymph 5. 

Blood 3.3 

Chyle 5-3 

Mucus 6 

Aqueous  Humor 11 

Vitreous 14 


Origin  and  Discharge. — It  is  introduced  with  the  dif- 
ferent kinds  of  animal  and  vegetable  food  and  fluids,  and  as 
a  condiment.  Being  soluble,  it  is  taken  up  by  absorption 
from  the  intestines,  and  is  deposited  in  different  parts  of  the 
body.  About  |  is  discharged  from  the  body  in  the  urine, 
fiieces,  perspiration  and  mucus,  the  remaining  J  being  sup- 
posed to  be  changed  in  the  body  by  double-decomposition 


lA 


18 


riiOXIMA riC   PRIACIPLES. 


with  ])ota.s,siuni  phosphate,  resulting  in  the  formation  of 
sodium  phosphate  and  potassium  chloride.  It  is  also  sup- 
posed to  furnish  the  sodium  to  all  the  salts  of  that  metal. 

^U^XTIUN. — It  rejjulates,  to  a  certain  extent,  the  process 
of  osmosis,  for  we  know  that  a  solution  of  sodium  chlo- 
ride i)ermeates  an  animal  membrane  nnich  less  readily 
than  pure  water.  In  tlie  blood  it  holds  in  solution  the  albu- 
men and  earthy  phosphates,  and  preserves  the  integrity  of 
the  blood  corpuscles.  As  an  article  of  diet,  it  stimulates  the 
secretion  of  saliva  and  gastric  juce,  and  aids  in  digestion. 
The  importance  of  sodium  chloride  in  this  respect  has  been 
demonstrated  by  Boussingault  in  the  fattening  of  animals. 
A  small  herd  of  animals  were  experimented  upon,  all  of  the 
same  age,  size  and  vigor.  They  were  divided  into  two  lots 
and  all  su])plied  with  an  abundance  of  nutritious  food.  One 
of  these  lots  was  deprived  of  this  salt  (except  what  was  con- 
tained in  the  food),  while  the  other  received  about  oOO 
grains  per  day.  No  difi'erence  was  observable  for  four  or 
five  months ;  from  that  time  to  the  end  of  the  year  a  marked 
difference  was  noticed.  Those  animals  which  received  the 
sodium  chloride  had  a  fine,  sleek,  healthy  aspect,  contrast- 
ing strongly  with  the  listless  and  inanimate  appearance  of 
the  others.  The  animals  of  the  forest,  as  the  buffalo  and 
deer  have  their  "  salt-licks  "  to  which  they  resort  from  time, 
to  time. 

Potassium  Chloride,  KCl. — This  substance  is  found  in 
the  muscleSjliver,  milk,  chyle,  blood,  gastric  juice,  bile,  saliva, 
mucus  and  urine,  as,sociated  with  .sodium  chloride.  It  is 
quite  soluble  in  the  fluids,  and  is  more  abundant  in  muscle 
and  milk,  than  sodium  chloride,  less  so  in  blood,  gastric 
juice  and  perspiration. 

Origin  and  Discharge. — It  is  introduced  with  the  food 
and  is  also  supposed  to  be  formed  in  the  interior  of  the  body 
by  double-decomposition  as  previously  stated.  Potassium 
chloride  is  discharged  in  the  urine,  mucus  and  perspiration. 

Function. — Its  function  is  probably  identical  with  sodium 
chloride. 


PROXIMA  TK  PRhXClPLKS. 


10 


Lime  Phosphate,  Ca^P^Og.  —  Lime  phosphate  is  found 
in  all  the  solids  and  fluids  of  the  body,  but  is  more  abun- 
<lant  in  the  solids,  and  increases  as  age  advances.  It  exists 
in  a  solid  state,  as  in  the  teeth,  bones ;  and  also  in  a  fluid 
state,  as  in  the  blood.  It  is  insoluble  in  water  ;  but  is  hold 
in  solution  in  the  fluids  of  the  body  by  albumen  and  the 
alkaline  chlorides,  In  the  urine,  is  is  hold  in  solution  by 
the  acid  sodium  biphosphate,  so  that  when  the  urine  is 
rendered  alkaline  the  phosphates  form  a  turbid  precipitate. 
In  bone  or  cartilago,  it  does  not  exist  as  a  granular  powder, 
but  is  intimately  united  with  the  animal  matter,  and  may 
be  dissolved  out  by  maceration  in  dilute  muriatic  acid, 
leaving  behind  the  animal  substance.  When  a  long  bone 
like  the  flbula  is  immersed  in  this  way  for  some  time,  it 
loses  its  brittleness,  and  may  be  bent  double,  or  tied  in  a 
knot,  without  breaking.  If  immersed  in  a  solution  of  lime 
carbonate,  its  rigidity  may  be  again  restored  to  a  certain 
extent. 

QUANTITY   OF   LIME   PHOSPHATE   IxV    1,000   PARTS. 


f  Uiine 7 

I  Milk 2.7 


f  Enamel 885. 

oj  I  Dentine 643. 

Is  -j  Done 550. 

;^      Cartilage 40.     t^   j  IJlood 3 

L  Muscle 2.5        l  Saliva 6 


"2  \  Gastric  Juice 4 


Origix  and  Discharge. — This  substance  is  derived  ex- 
clusively from  exterior  sources.  It  .  introduced  with  the 
food,  in  nearly  all  forms  of  which  it  is  found,  and  is  elimin- 
ated by  the  urine,  pt'rspiration,  and  mucus ;  most  by  the 
urine,  a  small  quantit}'  only  by  the  fseces  and  pers})iration. 

Function. — Its  use  is  to  give  consistence  and  strength 
to  parts ;  for  example,  in  the  enamel  of  the  teeth,  which  is 
the  hardest  tissue  in  the  body,  it  is  most  abundant,  and  in 
dentine  more  abundant  than  in  bone.  Its  presence  in  milk 
is  subservient  to  the  growth  and  development  of  bone  in 
the  vounjj  of  the  mammalia. 

Lime  Carbonate,  CaCOs. — This  substance  exists  in  the 


1 

« 

• 

1 

• 

t 

I 

4 

( 

tt 

* 


20 


PROXIMATE   PRINCIPLES. 


bones,  teeth,  cartilage,  blood,  sebaceous  matter,  internal  ear 
(otoliths),  and  in  the  urine.  In  bone  it  is  not  so  abundant 
as  lime  phosphate,  the  proportion  being  about  113  parts 
in  1000.  It  is  held  in  solution  in  the  blood  and  urine  by 
the  free  carbonic  acid  and  alkaline  chlorides. 

Origin  and  Discharge. — It  is  introduced  into  our 
bodies  with  the  food  and  drink.  Spring  water  contains  a 
variable  amount,  held  in  solution  by  the  free  carbonic  acid 
which  the  water  contains. 

Function. — Its  function  is  analogous  to  that  of  lime  phos- 
])hate. 

Sodium  and  Potassium  Carbonates,  Na.^CO,j,  ^.pO.^. — 
Sodium  and  potassium  carbonates  are  found  in  the  bones, 
blood,  lymph,  saliva,  and  urine.  They  give  to  the  blood  its 
alkaline  reaction.  Claude  Bernard  has  shown  that  the 
alkalescency  of  the  blood  is  necessary  to  life  ;  for  if  a  mineral 
acid  be  injected  into  the  blood  of  a  living  animal,  so  dilute 
as  not  to  coagulate  the  albumen,  death  takes  place  before  its 
alkaline  reaction  has  been  completely  neutralized. 

Origin  and  Discharge. — They  are  introduced  in  small 
({uantities  in  the  food,  but  are  principally  formed  within  the 
body  by  decomposition  of  other  salts,  malates,  tartrates,  and 
citrates  of  the  alkaline  bases.  These  salts  when  introduced 
into  the  body  in  the  food  are  decomposed.  Their  organic 
acid  is  destroj'ed  and  replaced  by  carbonic  acid,  forming 
sodium  and  potassium  carbonates.  They  aie  discharged  in 
the  urine  and  mucus. 

Function. — Their  function  is  to  maintain  the  fluidity  of 
the  fibrin  and  albumen,  to  give  alkalescency  to  the  blood 
and  secretions  and  to  assist  in  preserving  the  form  and  con- 
sistence of  the  blood  corpuscles. 

Sodium  and  Potassium  Phosphates,  Na2HP0_,,  K.^HPO^, 
— These  substances  exist  in  all  the  solids  and  fluids  of  the 
body.  They  are  soluble  in  water,  possess  an  alkaline  reaction 
and  are  known  as  the  aUcaline  phosphates.    These,  together 


with  tl 
of  the  I 
])0ssesK 
acid; 

The 
derane( 
deranct 
phospli 
nivora 

Orig 
food,  bfl 
in  the  1 
with  th 
perspira 

FUNC 

give  to  t 
conditio 
bonic  ac 
the  luno; 
water,  ei 
bonic  aci 
The  ai 
to  that  f 
phosphai 
portion  ( 

SODIU 

These  ex 
as  in  mi 
milk,  sali 
more  abi 
a  little  n 
are  intro 
also  form 
l)hates,  b 
with  the 


r  ROM  MA  TE  PRINCirUiS. 


21 


with  the  alkaline  cail»onate.s  are  essential  to  the  maintenance 
of  the  alkaline  character  of  the  fluidH  of  the  body,  all  of  which 
pos.sesji  an  alkaline  reaction  except  the  following,  which  are 
acid; 

1  (lastric  juice.  3  Urine. 

2  Perspiration.  4  Mucus  of  the  Vagina. 

The  fluids  of  the  carnivorous  animals  contain  a  prepon- 
derance of  the  alkaline  phosphates;  the  herbivorous  a  prepon- 
derance of  the  carbonates.  The  forjuer  is  owing  to  the 
phosj)hates  found  in  the  animal  tissues  upon  which  the  car- 
nivora  feed. 

Origin  and  Discharge. — They  are  introduced  in  the 
food,  both  animal  and  vegetable,  and  are  also  partly  formed 
in  the  body  by  the  oxidation  of  phosphorus  and  its  union 
with  the  alkaline  bases.  They  are  discharged  in  the  urine, 
perspiration  and  mucus. 

Function. — Together  with  the  alkaline  carbonates  they 
give  to  the  blood  and  secretions  their  alkaline  reaction.  This 
condition  of  the  blood  increases  its  power  of  dissolving  car- 
bonic acid,  and  also  favouis  the  elimination  of  the  latter  by 
the  lungs.  A  small  proportion  of  sodium  phosphate  added  to 
water,  enables  it  to  dissolve  twice  the  usual  quantity  of  car- 
bonic acid,  and  the  other  alkaline  salts  have  a  similar  action. 

The  acid  sodium  biphosphate,  is  found  in  urine,  and  gives 
to  that  fluid  its  acid  reaction.  It  is  formed  from  the  sodium 
phosphate  by  the  action  of  uric  acid  which  combines  with  a 
portion  of  the  sodium. 

Sodium  and  Potassium  Sulphates,  Na2S04,K2P04 — 
These  exist  in  small  quantity, — in  some  fluids  only  a  trace, 
as  in  milk,  saliva,  &/C,  They  are  found  in  blood,  lymph, 
milk,  saliva,  mucus,  perspiration,  urine  and  fjeces.  They  are 
more  abundant  in  the  urine,  than  in  any  other  fluid,  being 
a  little  more  than  half  as  much  as  of  the  phosphates.  They 
are  introduced  by  tne  food  and  drink,  A  certain  amount  is 
also  formed  in  the  body  in  a  similar  manner  to  the  phos- 
phates, by  oxidation  of  sulphur  and  its  subsequent  union 
with  the  alkaline  bases. 


c 


% 

% 


\ 

t 

« 
t 


H 


22 


PRO X IMA  TE  PK/NCIPLES. 


Magnesium  Phosphate  and  Carbonate,  MgHPO,,  Mg 
CO,. — These  salts  are  found  in  small  (quantities  in  nearly  all 
the  solids  and  fluids  of  the  body.  Associated  witli  lime 
phosphate,  they  are  known  as  the  earthy  phoHphate8, 
They  are  introduced  in  the  food.  They  are  dissolved  in 
the  fluids  by  the  alkaline  chlorides  and  phosphates,  and  in 
the  urine  by  the  sodium  biphosphate  The  salts  of  magne- 
sium are  more  abundant  in  muscles  and  brain, than  the  salts 
of  lime.  They  are  eliminated  principally  by  the  urine  and 
fseces. 

The  proximate  principles  of  the  first  class  exist  in  the 
animal  tissues  iii  (he;  same  form  in  which  they  occur  in  the 
inorga  lie  world.  Lime  carbonate  in  the  bones  is  the  same 
as  thai:  which  is  found  in  limestone  rock  ;  and  sodium  chlo- 
ride ic  similar  to  that  which  is  found  in  solution  in  sea 
water. 

Gases. — Oxygen,  nitrogen,  hydrogen,  carbonic  acid,  car- 
buietted  hydrogen  and  sulphuretted  hydrogen,  exist  in  a 
gaseous  state,  and  also  in  solution  in  some  of  the  fluids  of 
the  body. 

Oxygen  is  necessary  to  the  respiratory  process.  It  changes 
the  shape  of  the  blood  corpuscles  rendering  theia  biconcave, 
and  gives  to  the  arterial  blood  its  bright-red  colour.  Arte- 
rial blood  contains  about  10  to  12i  per  cent  of  oxygen. 
Nitrogen  exists  in  very  small  quantity  in  the  blood  and 
lungs.  It  is  also  found  in  the  intestines.  Carburetted  and 
sulphuretted  hydrogen,  also  pure  hydrogen,  are  found  in  the 
alimentary  canal,  and  in  small  quantities  occasionally  in 
expired  air.  Carbonic  acid  is  an  excretion  given  ofl'  prin- 
cipally by  the  lungs.  I'rom  20  to  25  per  cent,  is  found  in 
venous  blood. 

PROXIMATE   PRINCIPLES   OF   THE   SECOND    CLASS. 

The  substances  of  this  class  are  all  of  organic  origin,  and 
exist  both  in  vegetables  and  animals.  They  consist  of  car- 
bon, hydrogen  and  oxygen  only,  and  are  therefore  non-nitro- 


genous. 
fatty  mn 
the  proj) 
and  hy( 

Star 
lizable,  i; 
perties, 
crystalli2 
principle 
sesses  a 
the  flowc 
tapioca,  i 


In  Rice 

"  Maize. 
"  liarleyM 
"  Rye 
"  Oat 

Phy-sic. 
der,  consii- 
and  physii 
duces  a  cr, 
gers.  Eac 
gled  togetl 
is  more  at 
insoluble, 
to  j^7  of  i 
shaped  in  : 


round inor  a 
near  the  sn 
The  grar 
more  unifc 
to  50  mmm 
a  circulai-  p 
vary  from  ^ 
ameter,  nea 


PKOXIMA  TE  PK/NCIPLKS. 


'>3 


In 


genous.  There  are  two  divisions,  the  carbo-hydrates  and 
fatty  matters.  In  the  former  the  hydrogen  and  oxygen  are  in 
the  proportion  to  form  water,  and  in  the  latter  the  carbon 
and  hydrogen  arc  in  much  larger  quantity  than  the  oxygen. 

Stauch,  CjHioOs- — This  substance,  tliough  not  crystal- 
lizable,  is  so  closely  allied  to  the  others  in  its  general  pro- 
perties, and  so  easily  converted  into  sugar,  which  is 
crystallizable,  that  it  is  naturall}'  included  in  the  proximate 
principles  of  the  second  class.  It  is  not  amorphous,  but  pos- 
sesses a  distinct  granular  form.  It  is  found  in  nearly  all 
the  flowering  plants,  and  is  the  principal  ingredient  in  sago, 
tapioca,  arrowroot,  &c. 

(.)UANTITY  OF  STARCH  IN  100  PARTS. 


In  Rice 88 

"  Maize 67 

' '  Barley  Meal 66 

"Rye         "     64 

"  Oat  "     60 


Wheat  P'lour 57 

Iceland  Moss 44 

Beans 33 

Peas 37 

Potatoes 20 


Physical  Appearance  of  Starch. — It  is  a  white  pow- 
der, consisting  of  solid  granules,  which  vary  in  shape,  size, 
and  physical  appearance,  in  different  vegetables.  It  pro- 
duces a  crackling  sensation  when  rubbed  between  the  tiu- 
gers.  Each  starch  granule  consists  of  two  substances  niin- 
gled  together,  </?'anu^os6  and  cellulose.  The  former,  which 
is  more  abundant,  is  soluble  in  boiling  water,  the  latter  is 
insoluble.  The  starch  granule  of  potato  varies  from  yr^im 
to  T^T  of  an  inch  (2.5  to  G2.5  mmm.)  in  diameter,  is  pear- 
shaped  in  its  outline,  and  marked  by  concentric  rings  sur- 
rounding a  minute  pore,  called  the  hilum,  which  is  situated 
near  the  small  extremity  of  the  granule  (Fig.  1.) 

The  granules  of  arrowroot  are  oval  in  shape,  small,  and 
more  uniform,  and  vary  from  ^7/0-7  to  -jj-jy  of  an  inch  (12.5 
to  50  mmm.  j  in  diameter  (Fig.3).  The  hilum  is  in  the  shape  of 
a  circular  pore  or  transverse  slit.  The  starch  grains  of  wheat 
vary  from  jo  J  if  0  to  -,^00  o^  ^^  i^^ch  (2.5  to  35.5  mmm.)  in  di- 
ameter, nearly  circular  in  form,  with  a  round  or  transverse 


c 
{ 

t 


I  J 


( 

v 
k 
k 
t 
k 


24 


PROXIMATE  PRINCIPLES. 


hilum,  but  without  any  distinct  laminar  appearance  (Fig.  2), 
The  granules  of  Indian  com  are  the  same  size  as  the  preced- 
ing ;  they  are  irregular  in  shape,  and  present  a  crucial,  (Y)  or 
(T)  shaped  pore  (Fig.  4).  The  granules  of  rice  are  very  small, 
uniform  in  size,  polygonal  in  outline,  and  present  a  granular 
appearance  (Fii^.  o). 


Fi},'.  1  Starch  ttrunulojj  of  potato.     (2).  Staali  urrannles  of  wliuat.     (3).  Starch  ^^ranules 
of  arrowroot.    (4).  Starch  gniiiules  of  Indian  corn.    (f)).  Starcli  jfranules  of  rice. 

Origin  and  Properties. — It  is  found  in  most  vegetable 
substances  used  as  food,  and  in  that  way  is  introduced  into 
the  body.  It  is  also  found  in  the  animal  body  in  the  lateral 
ventricles  of  the  brain,  fornix,  and  septum  lucidum.  It  was 
first  observed  by  Purkinje,  and  afterwards  by  KoUiker  and 
Virchow.  The  granules  are  called  corpora  amylacea,  and 
Fige.  vary  in  size  from  ^-i^VTr  to  yiVo  of  8,n  inch 

(■)..')  to  22.5  mmm.)  in  diameter.  They  are 
transparent,  softer  than  in  vegetable  starch, 
incgularly  rotmded,  and  present  a  faint  lam- 
inar arrangement,  having  a  circular  pore  near 
the  centre,  with  lines  radiating  from  it — 

Corpora  A.nylacea,      Star-shapcd. 

Starch  is  insoluble  in  cold  water,  but  the  granules  swell 
out,  become  gelatinous,  and  are  readily  dissolved  in  boiling 


PROXIMATE  PRINCIPLES. 


25 


water.  It  is  then  said  to  be  hydrated.  This  is  simply  a 
mechanical  chaoge.  Starch  may  be  converted  into  dextHne, 
by  torrefaction— a  dry  heat  of  210°  (WO  F.)  This  sub- 
stance which  is  of  a  gummy  nature,  is  so  named  because 
in  solution  it  rotates  the  plane  of  a  polarized  ray  of  light 
towards  the  right. 

Starch  may  also  be  converted  into  sugar,  in  three  differ- 
ent ways. 

Firstly  J  by  boiling  in  dilute  nitric,  muriatic,  or  sulphuric 
acid  for  36  or  40  hours.  The  starch  is  first  converted  into 
dextrine  and  then  into  sugar,  and  at  the  same  time  loses 
its  property  of  responding  to  the  iodine  test. 

Secondly,  by  contact  with  an  animal  or  vegetable  sub- 
stance, at  a  temperature  of  37.5"  (100°F.)  Boiled  starch 
mixed  with  saliva  is  converted  into  sugar  in  a  few  minutes. 

Thirdly,hy  the  process  of  nutrition  and  digestion  in  ani- 
mals and  vegetables.  The  starch  found  in  seeds  and  roots 
is  converted  into  sugar  by  the  presence  of  diastase,  and  thus 
r'^ndered  soluble  before  it  can  be  taken  up  to  nourish  the 
plant  during  its  growth. 

Function. — Its  oiRce  in  the  animal  economy  is  to  form 
sugar.  Starch  is  converted  into  sugar  during  digestion  by 
the  action  of  the  pancreatic  and  intestinal  juices.  It  is 
necessary  foi-  the  process  of  development  and  nutrition  at 
all  periods  of  life.     It  is  the  source  of  sugar  in  the  vegetables. 

Test, — In  whatever  state  it  exists,  its  presence  may  be 
detected  by  its  reaction  with  free  iodine,  giving  a  blue 
color.  Ozone  test-paper  is  prepared  on  this  principle. 
White  paper  is  first  saturated  in  a  solution  of  starch,  and  then 
in  potassium  iodide.  When  exposed  to  an  atmosphere  con- 
taining ozono,  the  latter  oxidizes  the  potassium  and  liberates 
the  iodine  which  reacts  upon  the  starch,  and  stains  the 
paper  blue. 

Glycogen,  C^H^^Pj^ — This  is  the  name  given  to  an  amyla- 
ceous substance  found  in  animal  bodies.     It  exists  in  the 


I 


( 

i 

■r 

C 

ik«4 


1 
I 

1 


iim^ai±SS!^^ 


26 


PROXIMATE  PRINCIPLES. 


liver  of  all  vertebrate  animals,  also  in  the  muscles  and  in- 
tegument at  an  early  period  of  development.  It  gives  a 
violet-red  color  with  iodine,  instead  of  blue.  It  is  soluble  in 
water  and  is  easily  changed  into  sugar  or  glucose,  by  boil- 
ing with  a  dilute  acid,  or  by  contact  with  an  animal  sub- 
stance. It  is  the  source  of  sugar  formed  in  animals,  as  starch 
is  in  vegetables. 

Sugars. — These  substances  are  soluble  in  water,  crystal- 
lize on  evaporation,  and  are  converted  into  alcohol  and  car- 
bonic acid  in  the  process  of  fermentation.  The  ordinary 
vai'ieties  of  sugar  are  :  glucose  or  grape  sugar,  saccharose 
or  cane  sugar,  and  lactose  o\  milk  sugar.  Saccharose  is  more 
soluble  than  any  other  variety,  and  is  therefore  sweeter. 
Glucose  crystallizes  with  difficulty,  but  ferments  readily  ; 
while  cane  and  milk  sugar  ferment  with  difficulty.  Sugar  is 
necessary  in  the  process  of  nutrition  at  all  periods  of  life,  and 
is  also  supposed  to  assist  in  maintaining  the  animal  heat  of 
the  body.  It  is  never  discharged  from  the  body  in  health 
(except  in  the  female  during  lactation) ;  but  in  certain 
diseased  conditions  of  the  system,  it  is  rapidly  produced  in 
the  liver,  in  the  form  of  glucose  and  is  discharged  in  the 
urine,  constituting  d'mhetes  mellitits. 


TABLE   OF  QUANTITY   OF   SUGAR   IN   100   PARTS. 


In  Figs 62. 50 

II  Cherries 1^-52 

n  Peaches 1 1. 61 

M  Tamarinds 12.50 

It  Pears 11.52 

.,  Beets 8.00 

"  Barley 3.04 


Wlieat  Flour.. 
Rye  do. 

Ind'n  Corn  do. 

Peas 

Cow's  Milk. . . 
Asses  do. . . 
Human  do. . . 


2.33 
3-46 

3-71 
2.00 
5.20 
6.08 
6.50 


It  is  an  important  article  of  diet.  It  is  introduced  with 
the  milk  in  the  food  of  the  child.  In  the  adult  it  is  intro- 
duced partly  in  the  food  as  sugar  ;  but  mostly  in  the  form  of 
starch,  which  is  converted  into  glucose  during  digestion  by 
the  action  of  the  pancreatic  and  intestinal  juices. 

Glucose,  CgH^.^Oj. — This  variety  is  named  grape  sugar 
because   it   exists   in   large  quantity   in   ripe  grapes   and 


.^ 


sweet  fi 
in  the  ii 
foetus  di 
in  the  ] 
blood  in 
verted  ij 
a  moden 
boilinsr  ■' 
stances  a 
of  a  nitr< 
diastase. 
I'ests.- 
one  or  t\^ 
it  alkalin 
The  who] 
it  for  a 
suboxide 
precipitat 
blue.   .Th 
sugar  has 
in  the  pre 
neutralize 
to  cane  or 
phuric  aci( 
readily, 
mer's  test, 
tity  of  cof 
sufficient  s 
Organic 
test.     This 
removed, 
mate  princ 
"Fehlil 
as  in  Tron 
The  solutio: 

Copper  Si 
Potassium 
Sodium  hi 


PROXIMATE  PRINCIPLES. 


27 


sweet  fruits.  Glucose  is  found  in  the  interior  of  the  body, 
in  the  liver,  blood,  lymph,  chyle,  and  in  the  placenta  of  the 
foetus  during  the  first  three  months  of  foetal  life.  It  is  found 
in  the  portal  and  hepatic  veins,  but  disappears  from  the 
blood  in  its  passage  through  the  lungs,  being  probably  con- 
verted into  lactic  acid.  It  is  readily  soluble  in  water,  and  has 
a  moderately  sweet  taste.  It  may  be  formed  from  starch  by 
boiling  with  a  dilute  acid,  by  contact  with  animal  sub- 
stances at  a  temperature  of  37.50°  (100  F),  or  by  the  action 
of  a  nitrogenous  substance  in  a  state  of  decay,  as  vegetable 
diastase. 

Tests. — Trommer's  Test. — To  the  suspected  liquid  add 
one  or  two  drops  of  a  solution  of  copper  sulphate ;  render 
it  alkaline  by  the  addition  of  a  solution  of  caustic  potassa. 
The  whole  solution  then  assumes  a  blue  color.  Then  boil 
it  for  a  few  minutes,  and  if  sugar  be  present,  copper 
H^  suboxide  is  thrown  down  as  a  yellowish  or  reddish-brown 
precipitate.  If  no  sugar  be  present,  the  liquid  remains 
blue.  «The  principle  of  this  test  depends  upon  the  power 
sugar  has  in  reducing  the  copper  protoxide  to  the  suboxide, 
in  the  presence  of  an  alkali,  which  is  added  to  liberate  and 
neutralize  the  sulphuric  acid.  This  test  is  not  applicable 
to  cane  or  milk  sugar ;  but  by  boiling  them  in  dilute  sul- 
phuric acid  they  are  converted  into  glucose,  which  responds 
readily.  Liver  and  milk  sugar  act  promptly  with  Trom- 
mer's test.  Care  should  be  taken  that  only  a  small  quan- 
tity of  copper  sulphate  be  added,  as  there  might  not  be 
sufficient  sugar  in  the  solution  to  reduce  it. 

Organic  substances,  as  albuminose,  interfere  with  this 
test.  This  substance  may  be  precipitated  by  alcohol,  and 
removed.  Albuminose  will  be  described  among  the  proxi- 
mate principles  of  the  3rd  class. 

"  Fehling's  Liquor  "  Test. — The  principle  is  the  same 
as  in  Trommer's  test,  but  it  is  a  much  more  delicate  test. 
The  solution  is  prepared  according  to  the  following  formula : 


c 

\ 

«! 

•t 
I 


t 
t 

ir 

« 
C 


1  .. 


Copper  Sulphate,  crystallized 
Potassium  Tartrate,  neutral    .     . 
Sodium  hydrate  in  solution  sp.  gr. 


.  .  40  grammes  =(  617  grains) 
.  .  160  "  =-(2468  '«  ) 
1. 12  650        "         ={10029   "     ) 


28 


PROXIMATE  PRINCIPLES. 


The  first  two  are  dissolved  in  water,  mixed  with  the  alka- 
line solution  and  water  added  to  make  1154- -t  cubic  centi- 
metres =(^2  pints.) 

Add  to  the  suspected  mixture  enough  of  the  solution  to 
give  it  a  blue  tinge,  and  boil  If  sugar  be  present,  the  cop- 
per suboxide  is  thrown  down,  as  in  Trommer's  test.  A 
single  drop  of  this  liquid  will  detect  y'^  of  a  milligramme 
=(tA?t  of  i*-  grain)  of  glucose.  It  should  be  kept  excluded 
from  light  and  air,  otherwise  it  will  become  changed  and 
unfit  for  use. 

Fermentation  Test. — Add  a  few  drops  of  fresh  yeast  to 
the  saccharine  liquid,  and  keep  it  at  a  temperature  of  about 
25°  (77°F.),  in  this  way  the  sugar  is  converted  into  alcohol 
(C2HgO),and  carbonic  acid  (COg);  the  latter  should  be  collected 
in  a  vessel  and  examined.  Ever}'^  cubic  inch  of  carbonic 
acid  is  about  equal  to  one  grain  of  sugar.  The  presence  of 
carbonic  acid  may  be  proved  by  introducing  into  the  vessel 
a  lighted  taper,  which  will  be  immediately  extinguished;  or 
by  agitating  with  lime  water,  which  will  be  rendered  turbid 
by  the  formation  of  insoluble  lime  carbonate.  The  fer- 
mentation of  glucose  is  due  to  the  vegetation  of  a  micro- 
scopic fungus,  saccharoTYiyces  or  torula  cerevisioe.  The  fun- 
gus is  entirely  cellular,  the  cells  being  rounded  or  oval,  with 
one  or  two  nuclei  and  about  ^-^s^  of  an  inch,  (10  mmm.)  in 
diameter.  They  multiply  by  a  process  of  budding,  and 
occasionally  two  or  three  of  them  may  be  seen  adhering 
together.  They  may  be  observed  on  the  surface  of  diabetic 
urine,  which  has  stood  for  some  time.  They  break  up  after 
a  time  and  fall  to  the  bottom  of  the  vessel,  in  minute  oval 
spores. 

Moore's  Test,  or,  the  Potash  Test — A  little  caustic  pot- 
ash in  solution  is  added  to  the  suspected  liquid,  and  boiled 
in  a  test  tube.  If  sugar  be  present  it  acquires  a  brownish 
color.     This  is  not  a  very  reliable  test. 

Saccharose,  or  cane  sugar  CjgHggOjj. — Saccharose  is 
very  soluble,  readily  crystallized,  and  the  sweetest  of  all  the 


PROXIMATE  PRINCIPLES'  29 

sugars.  It  exists  in  the  sugar  cane,  maple,  beet,  parsnips, 
f'arrots,  turnips  etc.,  and  is  chiefly  used  for  culinary  purposes. 
It  is  formed  from  glucose  in  the  process  of  vegetation.  It 
will  thus  be  seen  that  starch  and  sugar  are  closely  allied  to 
each  other  in  all  their  relations — and  are  mutually  con- 
vertible, starch  being  the  solid  formation,  and  sugar  the 
active  liquid  one.  Cane  sugar  will  not  respond  to  Trom- 
mer's  test,  nor  ferment  until  it  has  been  transformed  into 
glucose  b}'  boiling  it  for  a  few  seconds  with  a  dilute  mineral 
acid,  or  by  adding  yeast  to  it. 

Lactose,  or  sugar  of  milk,  Cj2H240j2- — This  form  of 
sugar  is  found  only  in  milk,  and  is  a  constant  ingredient. 
It  is  less  soluble  than  the  other  forms,  and  therefore  not  so 
sweet.  It  undergoes  alcoholic  fermentation  slowly  and  in- 
completely, and  when  it  takes  place  in  milk  a  part  of  the 
sugar  13  transformed  into  lactic  acid — known  as  the  lactic 
acid  fermentation.  It  responds  readily  to  Trommer's  anl 
Fehling's  tests.  It  is  supposed  to  be  formed  from  glucose  by 
catalysis  in  the  mammary  gland. 

Oils  and  Fats. — These  substances  are  found  in  both 
animal  and  vegetable  tissues.  The  three  principal  varieties 
of  fat  which  exist  in  the  animal  economy  are :  Oleine — 
Cg^HjQ^Og ;  Margarine  or  Palmitine — Cg^H^gOg  ;  and  Stearine 
— CgyH^jQOg.  B^''  the  chemist  these  bodies  are  con- 
sidered as  salts,  formed  by  the  union  of  fat  acids  with  the 
base — glyceryl — thus  : — 

(  Oleic  Acid  (Ci8  H34  0-2  )  ) 
Oleine  . .  <        and  > Oleate  of  Glyceryl. 

(  Glyceryl  (C3  lis ) 

(  Palmiilc  Acid  (Cia  H32  O2  )  ) 
Palmitine  <  and  > Palmitate  of  Glyceryl. 

(  Glyceryl  (C3  H5 ) 

!  Stearic  Acid  {C18  H36  O2  )  ) 
and  > Stearate  of  Glyceryl. 

Gylceryl  C3  H5  ) ) 

These  may  be  separated  from  each  other  by  the  process  of 
saponification.  When  oleine,  palmitine,  or  stearine,  is  boiled 
in  a  solution  of  caustic  alkali,  it  is  decomposed  into  a  fat 
acid,  as  oleic,  palmitic,  or  stearic,  and  a  sweetish  viscid  fluid 


t 

\ 

fa 

s 

h 
I 


I- 

[ 

tt 

€ 

Si. 


30 


PROXIMA  TE   PRINCIPLED . 


the  hydrate  of  glyceryl,  or  glycerine.  The  acid  unitea  with 
the  alkali  and  forms  soap,  and  glycerine  (C^H^SHO.)  is  set 
free.  The  fat  acid  may  also  be  separated  from  the  base,  gly- 
ceryl, by  passing  steam  through  fat  at  a  temperature  of  300** 
(572°  F.)  The  human  body,  when  immersed  in  water  for  a 
length  of  time,  becomes  changed  into  a  substance  called 
adipocere,  or  saponified  fat.  This  is  supposed  to  be  a  pro- 
cess of  saponification,  caused  by  the  union  of  palmitic^ 
stearic,  and  oleic  acids  with  ammonia,  which  is  developed 
during  the  ])rocess  of  decomposition. 

Physical  Appearance  and  Properties  of  Fat, — It  ex- 
ists in  two  forms  in  the  body.  First,  in  the  form  of  large 
cells  or  vesicles,  varying  in  diameter  from  ^?,,.  to  ^?,o  of  an 
inch  (31  to  83  mmm.),  as  in  adipose  tissue,  (Fig.  9.)  Secondly^ 
in  the  form  of  oil  globules,  varying  from  ito.'mmt  to  jo'oo  of  an 
inch,  (1.2  to  G  mmm.)  as  in  the  chyle,  in  which  it  is  said  to  be 
emul^  ified,  (Fig  7.)  This  is  a  mechanical  subdivision  of  the  fat 


Fiu-, 


Fig.  8. 


Fa':  globules  of  chyle.  Fat  globules  of  cow 's  milk. 

cells,  and  is  the  only  form  in  which  it  can  be  absorbed.  Fats 
may  be  emulsified  by  means  of  alkalies,  serum  of  blood,  muci- 
lage, or  white  of  egg.  The  fat  cell  is  characterized  by  a  dark 
border  surrounding  a  bright  centre;  usually  no  nucleus  is  seen,, 
but  it  may  occasionally  be  found  attached  to  the  cell  wall. 
It  is  generally  rounded  in  shape,  but  is  found  irregular  in 
outline,  depending  on  pressure.  The  small  globules  appear 
as  minutely  dark  granules,  so  as  to  give  the  fluid  in  which 
they  float  an  opalescent  appearance.  In  cow's  milk,  the 
oil  globules  are  ^^'o^y  of  an  inch  (6.25  mmm.)  in  diameter,  have 
a  pasty   consistence,  due  to  the  palmitine  they  contain ; 


PROXIMATE  PRINCIPLES. 


31 


ftnd  when  churned,  are  converted  into  butter,  from  their 
tendency  to  cohere.  Oleine,  palmitine,  and  stearine,  are 
<always  found  mingled  together  in  the  body ;  but  they  are 
never  associated  with  any  of  the  other  proximate  principles 
of  the  bod}'',  as  water,  sugar,  ho,.  The  only  exception  is  the 
nerve  tissue,  in  which  they  are  combined  with  albumen,  and 

Fiu:.  9. 


Fat  cells  of  adipose  tissue. 

also  in  the  bile  dissolved  in  the  salts.  They  are  united  with 
phosphorus,  constituting  the  phosphorized  fats  of  nerve  tis- 
sue. This  union  is  supposed  to  take  place  in  the  lungs 
under  the  influence  of  oxygen.  In  the  living  body,  the  fats 
are  fluid,  or  nearly  so,  being  held  in  solution  by  oleine ;  but 
after  death,  they  assume  the  solid  condition.  Stearine  and 
palmitine  are  crystallizable,  and  sometimes  present  a  very 
beautiful  appearance.  The  crystals  are  needle-shaped,  and 
are  deposited  in  a  radiated  form,  but  sometimes  curved  and 
branching.  Stearine  predominates  in  hard,  palmitine  in 
soft,  and  (jleine  in  liquid  fats.  The  melting  point  of  stear- 
ine is  60°,  (14-0°  F.),  palmitine  46°,  (115°  F.),  and  oleine  38°, 
100°  F.  They  are  in.soluble  in  water,  but  are  .soluble  in 
ether  and  hot  alcohol. 

TABLE  OF  (QUANTITY  OF  FAT  IN  100  PARTS. 

Linseed 22.00  Cow's  milk 3. 70 

Eggs 7.00  Human  "   3.55 

Liver  of  calf. 5.58  Ikans 2.50 

Beef,  average 5. 19  Wheat 2. 10 

Salmon 4.85  Potatoes li 

Goat's  milk 3.82  Indian  Corn 9 


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32 


PROXIMATE  PRINCIPLES. 


FiK'.  10. 


Origin  and  Function. — It  is  found  in  all  parts  of  the 
body  except  in  the  compact  tissue  of  the  bones,  teeth,  ten- 
dons, beneath  mucous  membranes,  in  the  cutis,  between  the 
rectum  and  bladder,  beneath  the  epicranial  aponeurosis,  iti 
the  ligaments,  scrotum  and  eyelids.  It  is  introduced  in  the 
food,  and  is  emulsified  by  the  pancreatic  juice  during  diges- 
tion and  previous  to  absorption.     It  is  also  formed  in   the 

interior  of  the  body.  This  has  been 
proved  by  experiments  on  geese,  the  re- 
sult of  which  showed  more  fat  in  the 
body  than  could  be  accounted  for  by 
that  which  existed  in  the  food.  Another 
proof  is,  that  it  has  been  found  in  the 
form  of  globules  in  the  interior  of  the 
costal,  laryngeal,  and  tracheal  cartilage 
cells,  and  also  in  the  muscular  fibre  cell 
of  the  uterus  during  involution  (Fig.  10,) 
It  also  exists  in  the  form  of  globules  in 

uterine  muscular  fibre  cells.  *^6    ^^P^^^«    ^^^^^^      ^^^S'      ^^^     SebaCCOUS 

two  weeks  after  piirturitioii  glauds,  corpus  luteum  and  uriniferous 
tubes  of  the  carnivora.  In  the  marrow  of  bones,  it  exists 
both  in  the  form  of  oil  globules,  and  fat  cells  forming  adipose 
tissue.  In  some  parts,  it  is  formed  from  blastema  supplied 
by  the  blood  vessels,  as  in  adipose  tissue;  in  others  it  is 
formed  as  the  result  of  a  retrograde 
metamorphosis,  as  in  the  muscular 
fibre  cell  of  the  uterus. 

It  accumulates  in  excess  in  cer- 
tain diseased  conditions,  as  in  fatty 
degeneration  of  the  heait,  liver, 
kidney.  Its  function  in  the  foim  of 
adipose  tissue,  is  to  give  rotundity  to 
the  body ; form  a  nidus  for  delicate  organs;  fill  up  spaces  other- 
wise unoccupied,  and  from  being  a  bad  conductor,  to  prevent 
the  too  rapid  escape  of  the  animal  heat  of  the  body.  As  an 
article  of  diet,  it  is  necessary  in  the  process  of  nutrition.     It 


Fijf.  U. 


Hepatic  culls. 


PROXIMATE  PRINCIPLES. 


83 


supplies  animal  heat,  and  is  a  store  of  food  in  case  of  emer- 
gency, as  in  the  hybernating  animals.  Certain  kinds  of  food 
favor  the  formation  of  fat ;  for  example,  negroes  employed 
in  making  sugar  grow  fat  from  the  quantity  of  sugar  they 
eat.  It  is  said  to  accumulate  more  rapidly  when  the  animal 
is  fattened  in  a  darkened  room.  Fat  is  absorbed  from  the 
body  in  some  diseases,  and  its  place  supplied  with  serum,  as 
in  consumption.  It  is  discharged  by  the  sebaceous  glands 
of  the  skin,  and  in  the  milk  of  the  female  during  lactation. 

CholesteuinEjCojjH^^O. — Thissubstance  may  be  described 
among  the  oils  and  fats.  It  is  found  in  bile,  blood,  liver, 
nervous  tissue,  crystalline  lens,  and  meconium.  It  differ? 
from  ordinary  fat  in  the  fact  that  it  is  not  capable  of  saponi- 
fication, is  volatile  at  a  high  temperature  and  rotates  a  ray 
of  polarized  light  to  the  left.  It  crystallizes  in  thin  trans- 
parent rhomboidal  plates,  is  insoluble  in  water,  but  soluble 
in  ether,  chloroform,  hot  alcohol,  and  volatile  and  fatty  acids. 
When  treated  with  sulphuric  acid  and  chloroform  it  produces 
a  peculia..^  red  color,  which  soon  changes  on  exposure  to  air 
to  violet,  blue,  green  and  finally  fades  away.  It  melts  at 
14.5°  (293°F)  and  distils  at  3G0°.  (G8()^  F). 

PROXIMATE  PRINCIPLES  OF  THE  THIRD  CLASS. 

The  substances  belonging  to  this  class  are  very  important 
as  they  have  an  intimate  connection  with  the  active  phe- 
nomena of  living  bodies.  They  are  not  crystallizable,  and  are 
not  definite  in  their  chemical  composition  ;  that  is,  they  do 
not  always  contain  the  same  proportions  of  oxygen,  hydro- 
gen, carbon,  and  nitrogen,  but  the  relative  quantities  of 
these  elements  may  vary,  within  certain  limits,  in  different 
individuals,  and  in  the  same  individual  at  different  times, 
without  changing  in  any  material  degree  the  peculiar  pro- 
perties of  the  substance  which  they  form.  This  is  charac- 
teristic of  organic  substances.  They  all  closely  resemble 
albumen,  hence  called  "  albuminoid  substances".  Their  re- 
action is  neutral.     They  were  regarded  by  Mulder  as  com- 


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34 


PROXIMA  TE   PRINCIPLES. 


pounds  of  a  theoretical  radical,  which  he  called  protein. 
This  gave  them  the  name  of  "  protein  compounds".  The 
albuminoid  substances  are  all  hygroscopic.  In  some  parts  of 
the  body  they  are  fluid,  and  in  others  semi-solid,  or  solid, 
depending  upon  the  amount  of  water  which  they  contain. 
When  subjected  to  evaporation  they  lose  water,  and  may  be 
leduced  to  a  solid  state.  Advantage  is  taken  of  this  fact  in 
the  preservation  of  eggs,,  milk  etc ,  by  evaporating  at  a  low 
temperature  and  hermetically  sealing  in  cans.  When  water 
is  added,  they  again  absorb  it,  and  return  nearly  to  their 
original  condition. 

They  are  all  capable  of  being  coagulated.  Fibrin  coagu- 
lates spontaneously,  when  removed  from  the  vessels ;  albu- 
men, on  the  application  of  a  temperature  of  71°  (1G0°F.) ; 
and  casein  on  the-  addition  of  an  acid.  An  organic  sub- 
stance, once  coagulated,  cannot  be  restored  to  its  original 
condition.  It  may  be  dissolved  by  certain  re-agents,  as  e.  g., 
the  caustic  alkalies  ;  but  in  this  it  only  suffers  a  still  further 
alteration  ;  nevertheless  it  is  necessary  to  resort  to  coagula- 
tion to  remove  an  organic  substance  from  the  other  proxi- 
mate principles  with  which  it  is  associated.  FiVjrin  is 
obtained  by  switching  freshly-drawn  blood  with  a  bundle  of 
twigs.  Thus  obtained  it  is  an  unnatural  condition,  having 
lost  its  original  character  of  fluidit}^ 

These  organic  substances,  when  the  vital  force  is  removed, 
are  liable  to  putrefaction.  This  process  is  peculiar  to  organic 
nitrogenized  substances,  and  distinguishes  them  from  all 
other  proximate  principles.  When  in  a  state  of  putrefac- 
tion, they  are  capable  of  inducing  in  certain  other  substances 
a  process  of  fermentation,  as  for  example,  the  decaying  or- 
ganic matters  of  the  grape  give  rise  to  fermentation  of  the 
sugar,  converting  it  into  alcohol  and  carbonic  acid.  The 
putrescent  body  is  called  a  ferment,  and  acts  by  catalysis, 
or  by  its  mere  presence,  having  nothing  to  do  chemically 
with  the  process.  The  conditions  necessary  to  putrefaction 
are,  the  presence  of  oxygen,  heat,  and  moisture.     If  oxygen 


PROXIMATE   PRINCIPLES. 


85 


be  excluded  by  boiling,  and  the  substance  be  placed  in  her- 
metically sealed  vessels,  in  an  atmosphere  of  carbonic  acid, 
or  nitrogen,  putrefaction  will  not  take  place.  The  same  is 
the  case  if  the  substan  ',e  be  dried,  or  if  the  temperature  bo 
kept  near  the  freezing  or  boiling  points  respectively. 

During  the  process  of  putrefaction,  there  will  be  observed 
swarms  of  minute  microscopic  organisms  floating  about  in 
the  fluid,  called  bacteria  and  micrococci,  ^"i'■'  12 

(Fig.  12) ;  the  former  are  so  named  from 
their  rod-like  form,  and  consist  of  two 
small  cells  placed  end  to  end  ;  the 
latter  are  so  called  because  of  their 
minuteness,  and  appear  like  small 
specks.  Both  are  in  a  state  of  inces- 
sant and  rapid  motion.  Bacteria  are  in- 
creased by  spontaneous  subdivision  of   A.-Bactcrin.    n. -Micrococci. 

the  cell  into  two,  each  of  them  again  subdividing,  and 
so  on.  The  variety  found  in  putrefying  infusions  is  known 
as  the  hacteriwni  termo.  They  are  believed  by  some  to  be 
vegetable  organisms,  which  are  spontaneously  developed  in 
the  albuminoid  substance,  and  cause  putrefaction  to  take 
place.  By  others,  they  are  supposed  to  be  derived  from 
germs  floating  in  the  air,  and  which  become  developed  in 
putrefying  substances. 

Albuminous  matters  are  found  in  most  substances  used  as 
food,  the  proportion  according  to  Payen  being  as  follows  : 

QUANTITY  OF  ALBUMINOUS  MATTER  IN  100  PARTS. 


Beans 24.40 

Mackerel 24.30 

Peas 23.80 

Beefsteak 19-50 

Wheat 18.00 

Oats 14-30 


Oysters 14.00 

Salmon 1 3-  So 

Indian  corn 12.50 

Eggs 12.30 

lUce 7.50 

Potatoes 2. 50 


Albumen. — This  substance  is  named  albumen  from  "Al- 
bus,"  white,  on  account  of  its  appearance  when  coagulated. 
It  exists  both  in  the  fluid  and  solid  state  in  the  body — fluid 
in  the  blood,  lymph,  chyle,  cerebro-spinal  fluid,  serous  and 


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PROXIMATE  PRINCIPLES. 


synovial  fluids,  and  milk, — solid  in  tho  brain,  spinal  cord 
and  nerves.  It  is  also  found  in  mucous  membranes,  muscu- 
lar tissue,  and  in  tho  a(iueons  and  vitreous  humors  of  the 
eye.  It  exists  in  tho  white  of  Qgg,  and  can  bo  easily 
coagulated  or  ma<lo  to  assume  a  solid  form. 

Composition  and  Propeuties. — The  average  chemical 
composition  of  the  albuminous  substances  is  as  follows  : — 
(Fremy,) 

Carbon  ....  52.0 
Hydrogen  .  .  .  .6.9 
Nitrogen  .         .         .         .  15.6 

Oxygen  ....  24.0 
Sulphur  ....  1.5 

Albumen  does  not  coagulate  spontaneously,  but  may  be 
coagulated  by  any  of  tlie  following  re-agents,  viz.,  heat 
at  71°  (IGOT.),  alcohol,  mineral  acids,  as  nitric,  sulphuric, 
etc.,  tannic  acid,  potassium  ferrocyanide  in  an  acid  solution, 
and  the  metallic  salts.  It  is  vary  readily  coagulated  by 
bichloride  of  mercury,  and  hence  it  is  used  in  cases  of  poi- 
soning from  that  salt.  It  unites  with  it  to  form  the  so-called 
albuminate  of  mercury.  The  white  of  one  egg  is  sufficient 
to  neutralize  four  grains  of  the  bichloride.  Albumen  coag- 
ulates at  the  negative  pole  of  the  battery,  if  not  too  strong 
a  current,  and  at  both  poles  when  a  strong  battery  is  used. 
It  is  not  coagulated  by  the  vegetable  acids, except  tannic  acid. 
The  fresh  juices  of  vegetables  contain  a  substance  coagu- 
lated by  heat,  called  vegetable  albumen. 

When  albumen  is  evaporated  at  a  temperature  of  49°  (102° 
F.)  it  becomes  solid  and  brittle,  but  otherwise  unchanged,  and 
may  be  re-di.ssolved  in  water.  When  coagulated  by  heat  or 
the  mineral  acids,  &;c.,  it  cannot  be  re-dissolved  or  made  to 
resume  its  original  condition.  It  is  held  in  solution  in  the 
body  by  sodium  chloride,  sodium  and  potassium  carbonates 
and  phosphates,  which  give  it  an  alkaline  reaction.  It  ex- 
ists in  a  neutral  state  in  diseased  blood,  the  egg,  renal, 
splenic  and  hepatic  veins.  It  parts  with  some  of  the  soda 
in  passing  through  the  spleen,  kidney,  and  liver. 


Ill 

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PROXIMATE  PRINCIPLES. 


OuiaiN  AND  Function. — It  is  derived  from  the  albumin- 
oid elements  of  the  food,  by  a  ct.«.alytic  process  during 
digestion.  It  is  the  nutrient  element  of  the  blood,  and  the 
pabulum  of  all  the  tissues.  When  it  is  withheld  from  the 
food,  or  withdrawn  from  the  body  in  disease,  as  in  album- 
inuria, the  nervous  and  muscular  tissues  suffer  most.  It  is 
converted  into  fibrin  throuj^h  the  agency  of  the  blood-cells 
and  oxygen  ;  this  is  probably  a  chemico-vital  process.  Al- 
bumen is  never  discharged  from  the  body  in  health. 
In  a  diseased  state  of  the  kidney  it  is  found  in  the  urine, 
as  in  Bright's  disease,  also  in  scarlatina,  diphtheria,  and  in 
the  cold  stage  of  cholera. 

Tests. — These  depend  on  its  property  of  coagulation. 

first.  Heat. — When  a  solution  containing  albumen  is 
heated  in  a  test  tube  to  75°  (1C7°F),  a  precipitate,  more  or 
less  abundant,  is  formed.  If,  however,  the  liquid  be  alkaline 
the  albumen  will  not  coagulate  ;  hence  an  acid,  as  acetic  acid, 
should  be  used  to  neutralize  it.  The  earthy  phosphates  of 
the  urine,  when  in  excess,  are  thrown  down  by  hea- ,  but 
these  may  be  distinguished  from  albumen  by  the  addition 
of  a  few  drops  of  hydrochloric  acid,  which  clears  up  the 
phosphates,  but  has  no  action  on  the  albumen. 

Secondly.  Nitric  Acid. — When  this  is  added  to  a  solu- 
tion containing  albumen,  a  precij^itate  is  instantly  formed. 
When  the  urater  ..re  abundant  in  the  urine,  nitric  acid  causes 
a  dej- jsition  of  uric  acid,  but  this  may  be  re-dissolved  by  an 
excess  of  nitric  acid. 

Albuminose  or  Peptone. — This  is  a  colorless  liquid 
found  in  the  chyle  and  blood.  It  differs  from  albumen  from 
the  fact  that  it  is  not  coagulated  by  heat,  nitric  acid,  or  potas- 
sium ferrocyanide.  It  is  coagulated  by  alcohol  in  excess, 
and  the  metallic  salts.  When  in  solution  in  the  gastric  juice, 
it  interferes  with  Trommer's  test  for  grape  sugar.  It  is 
found  in  the  stomach  and  intestines,  only  during  digestion. 
When  Trommer's  test  is  applied  to  a  saccharine  liquid  con- 
taining albuminose,  a  purple  color  is  produced  on  the  ad- 


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PROXIMATE  PRINCIPLES. 


^ition  of  the  re-agents,  and  when  boiled,  the  color  changes 
from  red  to  yellow,  but  no  copper  suboxide  is  thrown 
down.  This  test  may  be  made  to  apply,  by  evaporating  the 
solution  to  dryness,  and  making  an  alcoholic  extract,  then 
a  watery  solution  of  the  sugar  contained  in  the  extract  will 
respond  as  usual.  It  also  interferes  with  the  mutual  reac- 
tion of  starch  and  iodine,  no  blue  color  beiug  produced. 

Origin  and  Function. — It  is  formed  from  the  organic 
nitrogenized  elements  of  the  food,  as  fibrin,  albumen,  and 
casein,  etc.,  by  the  action  of  the  gastric  juice  during  the 
process  of  digestion.  It  is  absorbed  in  this  state,  and  is 
converted  into  albumen  in  the  blood.  It  is  much  more  easily 
absorbed  than  albumen,  on  account  of  its  superior  osmotic 
properties.  It  is  the  soluble  principle  of  fibrin,  albumen, 
casein,  &c. 

Fibrin. — Fibrin  exists  in  the  blood,  lymph,  and  chyle  as 
found  in  the  lacteals.  When  blood  is  removed  from  the  ves- 
sels, it  soon  separates  into  a  solid  portion,  or  clot,  and  a 
fluid  portion,  or  serum.     The  clot  consists 

Fig.  13. 


of  coagulated 


Coaj,'ulatetl  fibrin  containing:  white  blood  corpuscles.  i 

fibrin,  containing  red  and  white  corpuscles  entangled  in  its 
meshes.  When  inflammation  is  present,  the  red  corpuscles 
have  a  tendency  to  cohere,  and  sink  to  the  bottom  of  the  vessel, 
hence  the  fibrin  is  more  abundant  at  the  top,  and  from  the 


PROXIMATE  PRINCIPLES. 


SD- 


peculiar  color  it  presents,  is  called  the  "  buffy  coat."  Fibrin 
is  difficult  to  obtain  free  from  corpuscles.  It  may  be  ob- 
tained nearly  pure,  by  switching  freshly-drawn  blood  with  a 
bundle  of  twigs.  It  coagulates  on  the  twigs,  and  may  be 
freed  from  impurities  by  washing.  It  is  first  washed  with 
water,  to  remove  the  salts,  then  with  alcohol,  to  remove  the 
pigment,  and  ether,  to  remove  fatty  matters.  Another 
mode  is  to  filter  frogs'  blood,  the  corpuscles  of  which,  being 
large,  are  kept  back  ;  but  the  liquor  sanguinis  passes  through, 
and  the  fibrin  coagulates,  and  may  be  washed  as  above.  A 
little  thin  syrup,  or  a  weak  solution  of  an  alkali,  should  be 
added  to  retard  coagulation  during  filtration.  It  is  some- 
times found  in  a  tolerably  pure  state,  in  the  cavities  of  the 
heart  and  large  arteries  after  death.  It  is  also  found  arranged 
in  lamina3,  in  the  sacs  of  aneurisms.  It  is  regarded  by 
some  as  formed  by  the  union  of  two  substances  in  the  blood, 
fibrinogen  and  fibrinojilastin,  and  by  others  as  resulting  from 
the  decomposition  of  a  substance  called  plasmine. 

Physical  Appearance  and  Properties. — Fibrin  is  a 
greyish- white,  tough,  elastic  and  stringy  substance,  composed 
of  microscopic  fibrils.  It  possesses  the  property  of  "  spon- 
taneous coagulation,"  or  fibrillation.  It  is  insoluble  in 
water,  alcohol,  and  ether,  but  is  soluble  in  the  alkalies. 
Three-fourths  of  its  weight  is  water.  When  treated  with 
acetic  acid,  it  swells  out,  becomes  soft  and  gelatinous,  and 
slightly  soluble  in  water.  It  may  be  dissolved  in  cold  con- 
centrated hydrochloric  acid,  and  after  a  time  the  solution  ac- 
quires a  blue  color.  When  dissolved  in  the  potash  salts,  it 
resembles  albumen  in  its  properties  and  reactions.  When 
boiled  in  water,  it  forms  binoxide  and  teroxide  of  protein. 
When  boiled  in  hydrochloric  acid,  it  yields  "  leucine  "  and 
"  tyrosine."  It  is  held  in  solution  in  the  blood  by  the  alka- 
line chlorides  and  carbonates. 

Coagulation. — The  coagulation  of  fibrin  is  a  process  of 
fibrillation.  When  the  process  of  coagulation  is  viewed  with 
a  microscope,  a  granular  appearance  is  first  noticed  ;  some  of 


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40 


PROXIMATE  PRINCIPLES. 


the  granules  become  star-shaped  by  the  addition  of  other 
granules,  the  arms  being  directed  towards  the  corpuscles 
which  are  ultimately  included  in  the  meshes.  When  fully 
organized  it  is  distinctly  fibrous  in  structure,  ooagulation  of 
the  fibrin  takes  place  more  slowly  in  the  absence  of  the 
corpuscles,  as  in  filtered  blood.  Certain  vegetable  sub- 
stances as  wheat  flour,  contain  an  albuminous  matter  very 
similar  to  fibrin,  called  gluten,  or  vegetable  Jlbrin. 

Origin  and  Function. — Fibrin  is  formed  from  albumen, 
by  the  influence  of  the  corpuscles  and  oxygen ;  in  other 
words,  it  is  albumen  in  a  higher  state  of  organization.  It 
gives  to  the  blood  its  property  of  coagulation,  and  it  is 
through  this  property  that  "  natural  hsemostasis"  is  effected. 
It  gives  to  the  blood  its  viscidity,  and  prevents  it  from, 
exuding  through  the  coats  of  the  vessels.  It  was  formerly 
supposed  to  be  the  material  which  was  thrown  out,  and  sub- 
sequently became  organized,  in  the  repair  of  wounds,  and  in 
inflammation,  under  the  name  of  "  coagulable  lymph" 
Lymph  is  now  generally  believed  to  be  the  product  of  the 
white  corpuscles,  which  have  passed  through  the  coats  of  the 
vessels  by  virtue  of  their  amoeboid  movement,  supplemented 
by  the  proliferation  of  connective  tissue  elements  in  the 
wounded  or  inflamed  parts. 

Fibrin  was  by  some  considered  as  effete  matter,  formed 
from  the  worn  out  elements  of  the  blood  and  tissues,  and  the 
argumcniis  adduced  in  favour  of  that  view  were,  that  it  was 
increased  in  bleeding  and  starvation ;  that  there  was  none 
found  in  the  renal  veins,  having  been  discharged  by  the 
kidneys  ;  that  there  was  very  little  in  the  blood  of  the 
foetus  ;  none  in  the  egg ;  none  in  the  chyle  until  it  entered  the 
lacteals,  and  then  only  as  the  result  of  the  additions  made 
to  it  from  the  blood  or  lymph. 

Casein. — This  is  an  albuminous  principle  found  only  in 
milk.  It  is  held  in  solution  by  the  alkaline  carbonates,  and 
when  any  of  the  organic  or  mineral  acids,  or  magnesium 
tiulphate  is  added,  the  alkali  is  neutralized,  and  coagulation 


of 


PROXIMATE  PRINCIPLES. 


41 


of  the  casein  follows.  It  is  also  coagulated  by  a  solution  of 
rennet,  the  abomasus,  or  fourth  stomach,  of  the  young  of 
ruminants.  The  pepsine  contained  in  the  stomach  has  the 
power  of  converting  the  sugar  of  milk  into  lactic  acid, 
which  neutralizes  the  alkali,  and  causes  a  precipitate  of 
casein.  This  is  a  catalytic  process.  Casein  is  also  coagu- 
lated during  a  thunder  storm  ;  a  substance  called  ozone  is 
developed  in  the  atmosphere,  which  acts  on  the  casein  and 
decomposes  it.  The  decaying  casein  acts  as  a  ferment,  and 
converts  the  sugar  of  milk  into  lactic  acid,  which  precipi- 
tates the  casein.  Casein  differs  from  albumen  ;  it  is  not 
coagulated  by  heat,  and  is  precipitated  by  organic  acids. 
The  precipitate  of  casein  may  be  re-dissolved  by  a  solution 
of  caustic  alkali.  It  is  insoluble  in  water  and  alcohol.  An 
albuminous  substance  called  vegetable  casein  is  found  in 
beans,  peas,  &c. 

Origin  and  Function. — It  is  formed  from  the  albumen 
of  the  blood  by  a  catalytic  process  in  the  mammary  gland. 
It  has  been  found  in  the  blood  of  puerperal  women.  Casein 
may  be  obtained  in  a  nearly  pure  state,  by  precipitating  it 
with  acetic  acid,  and  then  washing  the  precipitate  witli 
alcohol  and  water.  It  is  the  chief  aliment  of  the  young  of 
the  mammalia,  and  the  substance  from  which  all  the  tissues 
are  formed. 

Globuline. — This  is  a  semi-solid  substance  found  in  the 
crystalline  lens,  in  the  blood  globules,  and  in  the  structure 
of  cells  generally.  It  is  coagulated  by  heat,  alcohol,  and  the 
mineral  acids.  It  is  soluble  in  water,  but  not  in  the  liquor 
sanguinis  of  the  blood.  The  coagulum  of  globuline  is  partly 
jjoluble  in  hot  alcohol ;  this  distinguishes  it  from  albumen. 
Acetic  acid  causes  it  to  swell  out  and  become  transparent. 
The  globuline  of  the  crystalline  lens  is  called  by  some 
"  Crystalline"    It  is  more  easily  coagulated  than  globuline. 

Pepsine. — This  is  the  organic  principle  of  the  gastric 
juice.     It  is  coagulated  by  heat  and  alcohol,  and  is  with 


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42 


PROXIMATE  PRINCIPLES. 


difficulty  distinguished  from  albumen.  It  exists  in  the 
gastric  juice  in  the  proportion  of  fifteen  parts  per  thousand, 
from  which  it  may  be  precipitated  and  extracted  by  means 
of  alcohol.  The  solvent  power  of  the  gastric  juice  depends 
on  the  presence  of  pepsine.  This  will  be  discussed  in  the 
chapter  on  digestion. 

Pancreatine. — This  substance  exists  in  the  proportion  of 
ninety  parts  per  thousand  in  pancreatic  juice.  It  is  a 
viscid  fluid,  coagulable  by  heat,  alcohol,  and  strong  acids. 
It  is  coagulated  by  magnesium  sulphate  ;  this  distinguishes 
it  from  albumen.  It  has  the  property  of  emulsifying  oils 
and  fats,  and  of  converting  starch  iiiiu  sugar  during  the  pro- 
cess of  digestion.  It  is  formed  from  the  albumen  of  the  blood 
in  the  pancreas. 

Ptyaline  is  an  ingredient  in  saliva,  and  gives  it  the  pro- 
perty of  converting  starch  into  sugar.  It  is  not  coagulated 
by  nitric  acid  or  acidulated  potassium  ferrocyanide.  This 
distinguishes  it  from  albumen.  It  is  precipatated  by  alco- 
hol and  boiling,  and  in  the  latter  case  loses  its  power  of  con- 
verting starch  into  sugar. 

Mucosine. — The  organic  substance  of  mucus  is  termed 
mucosine.  In  some  of  its  properties  it  resembles  albumen. 
It  is  coagulated  by  alcohol  and  acids,  but  not  by  heat,  or 
the  metallic  salts.  It  lubricates  the  free  surface  of  mucous 
membranes,  and  is  formed  from  the  blood  by  the  agency  of 
the  cells,  which  line  the  free  surface  of  the  membrane  and 
its  follicles. 

Musculine  or  Myosine  is  a  semi-solid  substance  peculiar 
to  muscular  tissue.  It  is  insoluble  in  water,  but  is  soluble  in 
a  mixture  of  ten  parts  of  water  with  one  of  hydrochloric 
acid,  and  may  be  precipitated  again  by  neutralizing  with 
an  alkali.  It  is  a  most  important  element  of  animal  food, 
and  is  the  great  source  of  albumen  and  fibrin. 

Cartilagine  is  the  organic  ingredient  of  cartilage.  By 
prolonged  boiling,  it  is  transformed  into  a  substance  called 


mal 


gi. 


PROXIMATE  PRINCIPLES. 


43 


COLLAGEN- 

liganients,  etc. 
mal   matter. 
"  L'elatine  "  or 


"  chondrine."     It  is  precipitated  by  acids  and  some  of  the 
metallic  salts  ;  this  distinguislies  it  from  "  gelatine." 

This  substance  is  peculiar  to  bones,  tendons, 
It  constitutes  the  principal  part  of  the  ani- 
By   prolonged  boiling,  it  is  converted  into 
"  glue,"  and  is  then  soluble  in  water. 

Elasticine. — This  is  the  organic  principle  of  the  yellow 
elastic  tissue.  It  is  not  soluble  in  water,  alcohol,  ether,  or 
acetic  acid,  but  is  dissolved  and  decomposed  in  nitric,  sul- 
phuric and  hydrocliloric  acids,  and  these  solutions  are  not 
preci))itated  by  alkalies. 

Keratine. — This  is  an  organic  substance,  found  in  the 
epidermis,  nails  and  hair.  It  is  not  affected  by  boiling  in 
water,  alcohol,  ether  and  dilute  acids,  except  by  continuous 
boiling  in  a  Papin's  digester  at  150°  (:302°F). 

COLORING   MATTERS. 

The  substances  of  this  group  give  to  the  tissues  and  fluids 
their  distinctive  coloration.  They  are  all  supposed  to  bo 
crystal lizable,  and  formed  from  the  coloring  matter  of  the 
blood.  The  coloring  matter  may  be  removed  from  the  fluids 
of  the  body  by  filtering  through  animal  charcoal,  which 
has  the  ])roperfy  of  removing  coloring  matter  from  any  fluid. 
Animal  charcoal  will  also  remove  albuminous  matter  from 
any  fluid  containing  it.  The  most  abundant  and  important 
of  the  coloring  matters  is 

Hemogi^ohine. — It  is  analogous  in  manj''  respects  to  chlo- 
rophyl  in  the  vegetable  kingdom,  for  while  hemoglobine  is 
the  agent  on  the  one  hand  by  which  oxygen  is  carried  into 
the  system,  chlorophyl,  on  the  other,  is  the  agent  by  which 
carbonic  acid  and  water  are  decomposed  and  oxygen  set 
free  in  the  vegetable.  It  exists  in  the  blood  corpuscles  in 
the  proportion  of  25  to  30  per  cent.,  and  also  in  muscular 
tissue.  It  is  soluble  in  water,  dilute  alcohol,  and  alkaline 
salts,  but  is  insoluble  in  strong  alcohol,  ether  and  oils.  It 
crystallizes  out  in  rhombic  or  hexagonal  plates  or  prisms* 
3 


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44 


PROXIMATE  PRINCIPLES. 


differing  in  different  species,  and  also  in  the  same  species 
under  different  circumstances.  It  is  easily  decompojed.  Its 
characteristic  property  is  its  great  power  of  absorbing  oxy- 
gen, which  it  holds  in  a  free  state,  until  it  yields  it  up  to 
the  tissues.  When  charged  with  oxygen  it  becomes  bright  red, 
and  is  called  "oxidized"  or  scarlet  hemoglohine ;  whendeoxi- 
dized,it  assumes  a  purple  color,and  is  called  "reduced"  or  pur 
pie  hemoglohine.  It  contains  4.2  parts  iron  per  thousand, 
which  is  essential  to  the  blood.  This  is  not  in  the  form  of 
an  oxide,  but  is  combined  with  carbon,  hydrogen,  nitrogen, 
and  oxygen  of  which  it  is  composed.  Iron  is  also  found  in 
the  coloring  matter  of  the  hair,  bile  and  urine.  The  blood 
of  an  ordinary  sized  man  is  said  to  contain  2.8  grammes  (43 
grs.)  of  iron.  When  the  red  blood  corpuscles  are  broken 
down  from  any  cause,  the  hemoglohine  is  set  free,  and  the 
walls  of  the  vessels  and  tissues  are  stained.  This  has  been 
mistaken  for  arteritis.  When  the  hemoglohine  is  deficient 
in  the  blood,  as  in  anemia,  etc.,  it  may  be  restored  by  the 
administration  of  iron. 

Melanine  is  a  brownish-colored  substance,  found  in  those 
parts  of  the  body  where  pigment  exists,  as  in  the  choroid 
coat  of  the  eye,  iris,  epidermis  and  hair.  It  is  very  abun- 
dant in  the  epidermis  of  the  negro.  It  is  formed  from 
hemoglohine,  but  contains  less  iron.  The  coloring  matter  is 
the  same  in  all  situations,  the  different  shades  being  pro- 
duced by  the  arrangement  of  the  pigment  cells  among  the 
fibres  and  capillaries  of  the  tissue.  In  some  cases  it  is 
entirely  absent,  as  in  the  "  albino."  It  is  insoluble  in  water 
alcohol,  ether  and  dilute  acids,  but  is  soluble  in  caustic 
potassa. 

BiLiRUBiNE  is  formed  from  hemoglohine  in  the  liver,  and 
constitutes  the  yellowish-red  coloiing  matter  of  the  bile.  It 
is  crystal lizable,  insoluble  in  water,  but  soluble  in  alcohol, 
ether,  chloroform,  and  alkaline  fluids.  It  responds  readily 
to  "  Gmelin's  bile  test," — nitroso-nitric  acid.  If  a  small  quan- 
tity of  nitric  acid  be  dropped  into  a  solution  of  bilirubine 


PROXIMATE  PRINCIPLES. 


45 


to  w^hich  nitrous  acid  is  previously  added,  a  play  of  colors 
is  produced  in  order  as  follows, — green,  blue,  violet,  red,  arul 
yellow.  Bilirubine,  if  rendered  alkaline,  and  exposed  to  tlie 
air  becomes  changed  into  biliverdine. 

BiLiVERDiNE  is  the  greenish  coloring  matter  of  the  bile. 
It  is  more  abundant  in  animals  that  feed  upon  vegetable 
food.  It  is  insoluble  in  water,  ether  and  chloroform,  but  is 
soluble  in  dilute  alkaline  solutions,  alcohol,  and  acetic  acid. 
It  is  believed  to  be  formed  from  bilirubine.  It  is  discharged 
from  the  body  in  the  faeces.   It  is  often  found  in  gall  stones. 

Urochrome  or  Urosacine  is  a  yellowish-red  coloring 
matter  peculiar  to  the  urine.  It  is  found,  also,  in  urinary 
calculi.  It  is  probably  the  worn-out  hemoglobine  of  the 
blood,  which  is  being  discharged  by  the  kidney.  Urosa- 
cine and  the  coloring  of  bile  arc  both  discharged  from  the 
body,  the  one  in  the  urine,  and  the  other  in  the  fieces.  It 
is  soluble  in  water  and  in  ether,  but  only  slightly  so  in 
alcohol. 

LUTEINE  is  a  yellow  coloring  matter  found  in  yolks  of 
eggs  and  the  corpus  luteum.  It  is  crystallizable,  insolu- 
ble in  water,  but  soluble  in  alcohol,  ether,  chloroform,  and 
oils.  It  is  easily  decomposed,  and  nitric  acid  added  to  it 
gives  a  blue  color. 

CRYSTALLIZABLE  NITROGENOUS  MATTERS. 

The  substances  of  this  group  are  crystallizable,  and  with 
one  or  two  exceptions  are  derived  from  the  nitrogenous  mat- 
ters of  the  body  as  the  result  of  retrograde  changes.  They 
are  lecithine,  cerebrine,  leucine,  and  the  substances  found  in 
urine  and  bile,  as  urea,  creatine,  creatinine,  urates  and  hippu- 
rates  of  soda,  glycocholate  and  taurocholate  of  soda.  The 
latter  will  be  described  with  urine  and  bile  respectively. 

Lecithine,  formerly  described  as  a  phosphorized  fat  is 
found  in  blood,  (.4  parts  per  thousand),  bile,  spermatic  fluid, 
yolk  of  egg  and  nerves,  also  in  certain  vegetables.     It  is 


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PRIMARY  FORMS  OF  TISSUE. 


Holuble  in  alcohol,  ether,  chloroform,  and  oils,  and  is  easily 
decomposed.  Water  swells  it  up  into  a  pasty  mass,  and  j^ives 
rise  to  so-called  "  niyeline  forms,"  an  appearance  resembling 
"  myeline  "  or  medullary  layer  of  nerve  fibre.  It  contains 
phosphorus. 

CLiREniiiNE  exists  only  in  brain  and  nerves,  and  is  more 
abundant  in  the  white  than  the  gray  substance.  It  is  a 
whitish  substance,  insoluble  in  water  and  ether,  but  is  solu- 
ble in  boiling  alcohol  and  deposits  again  on  cooling.  Heated 
in  the  air  it  turns  brown  and  burns  readily. 

Leucine  is  found  in  small  quantities  in  the  kidneys, 
si)leen,  liver,  pancreas,  brain  and  glandular  system.  It  crys- 
tallizes in  whitish  glistening  laminus  and  is  soluble  in 
water  and  alcohol,  but  insoluble  in  ether.  Little  is  known 
regarding  the  origin  and  physiological  relation  of  these  sub- 
stances. 


CHAPTER  IL 


ELEMENTARY   OR    PRIMARY   FORMS   OF   TISSUE. 

The  elementary  or  primary  forms  of  tissue  are  cells, 
granules,  simple  fibres,  and  simple  or  basement  membranes. 
Of  these,  the  cells  are  the  most  important,  since  they  are 
the  active  agents  in  the  performance  of  aiJ  the  functions  of 
the  animal  body,  as  digestion,  absorption,  selection,  assimi- 
lation, respiration,  secretion,  excretion  and  reproduction. 
They  also  constitute  the  fundamental  elements  of  all  the  tis- 
sues, and  are  the  active  agents  in  all  the  catalytic  and 
chemico-vital  changes  which  take  place  in  the  animal  eco- 
nomy. The  agency  of  cells  is  not  only  exhibited  in  the 
healthy  actions  of  the  body,  but  may  also  be  seen  in  the  de- 
velopment of  various  morbid  growths,  as  fibroid  tumors, 
cancer,  etc.  The  form  which  organic  matter  takes  when  it 
passes  from  the  condition  of  a  proximate  principle  to  that 
of  an  organized  structure,  is  that  of  a  cell,  a  simple  fibre,  or 
a  simple  membrane. 


PRIMARY  FORMS  OF  TISSUE. 


47 


In  all  animal  and  vegetable  tissues,  there  exists  a  soft 
gelatinous  or  albuminous  substance  called  'protoplaHrrit 
sarcode,  cytoplasm  or  "  (jervtlnal  mattev."  It  is  transparent, 
of  the  same  consistence  in  all  parts  of  the  body,  and  by  the 
action  of  the  vital  forces  may  be  formed  into  small  rounded 
masses  or  cells,  or  thin  hyaline  membranes.  It  possesses 
properties  and  exhibits  phenomena  which  are  called  vital, 
such  as  the  movement  of  molecules  in  its  substance,  and  the 
changes  in  the  shape  of  the  mass  itself. 

CELLS. 

A  cell  may  be  defined  to  be  a  semi-solid  rcjunded  mass  of 
protoplasm,  or  it  may  assume  the  form  of  a  membranous 
sac  enclosing  proto[)lasmic  or  other  contents.  In  the  in- 
terior of  most  animals  cells  will  be  seen  a  small  body 
termed  the  nucleus,jai,nd  within  the  nucleus,  a.  nucleolus ;  or 
there  may  be  two  or  more  nuclei,each  containing  one  or  more 
nucleoli. 

Vakiation  in  Shape. — Cells  are 
generally  globular,  but  may  as- 
sume various  shapes,  depending  on 
internal  and  extei'ual  circumstances, 
and  the  growth  of  the  cell ;  for  ex- 
ample, fat  cells  which  are  round 
when  formed,  may  become  poly- 
gonal as  the  result  of  mutual 
pressure  (Fig.  9.)  The  specific  gra- 
vity of  the  contents  will  also  atfect  i^} 
the  shape  to  a  considerable  extent,  clear -'ianrco 
When  water  is  added  they  have  a  ^gSef'^  '^'"'"^  corpuscle,  (k)  Fat 
tendency  to  swell  out  and  finally  burst.  When  evaporation 
or  desiccation  takes  place,  they  become  flattened  and  hard- 
ened, as  in  the  epidermis.  The  shape  of  the  cell  may  also 
be  changed  by  the  absorption  of  gases  and  vapors,  e.g.,  the 
blood  corpuscles  present  a  distinctly  biconcave  disk  under 
the  influence  of  oxygen,  and  become  rounded  again  when 


Fits.  14. 


Xcrve   cell.       (h)  -NucleoluB. 
(d)  Oaiiiflion  corpus- 
nuclei,     (e)     Multiiui- 
ccU  from  bone   marrow. 


)— Nucleus. 


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48 


PRIMARY  FORMS  OF  TISSUE. 


riu'int-iit  Cells. 


exposed  to  the  influence  of  carbonic  acid  gas.  The  vapor  of 
ether,  when  inhaled,  produces  an  irregular  appearance  of  the 
blood  corpuscles.  Chloroform  vapor  causes  a  serrated  out- 
line, and  alcohol  renders  them  oval,  with  an  indentation  on 
one  side. 

KiK.   1"'. 

Cells  may  also  assume  different 
shapes,  depending  on  their  growth  ; 
for  example,  the  pigment  cell,  which 
is  at  first  spheroidal,  throws  out  arms 
or  projections  in  different  directions, 
and  becomes  stellate  during  its 
growth.  The  nerve  cell  becomes  unipolar,  bipolai-,  or  multi- 
polar ;  nonstriated  muscular  cell,  fusiform.  Epithelial  cells 
are  either  cylindrical  (columnar),  or 
squamous  (tesselatcd  or  pavement.) 
In  some  instances,  hair-like  growths 
take  ])lace  on  the  free  surfaces  or  ex- 
tremities of  cells,  as  is  seen  in  thc| 
cilia  of  epithelial  cells.     Some  cells 

undergo  a  spontancoufi  change  in^^J,,,,,,^^  „,,i„.^,i„,„  ^^  t,,e 
shape,  as  the  amuilinj,  white  corpus- ^^^^  ^,;-'^;;^|;;;r^,iatc.)  qntueiium 
cles,  etc.  "'  ^'•'-'  "•""''• 

Variation  in  Size. — Cells  vary  in  size  from  ^i^  of 
an  inch  (83.5  mmm.)  in  diameter,  the  size  of  the  largest 
fat  cell,  to  ^ooo.)  of  an  inch,  (1.25  mmm.)  the  size  of  the 
fat  globule.  Some  are  so  large  as  to  be  called  giant 
cells,  as  those  of  bone  marrow  (Fig.  14,  e.),  and  abnormal 
tumors,  as  cancer,  sarcoma,  etc.  The  average  diameter  of 
the  red  blood  corpuscle  is  about  ^-aVo  of  an  inch,  (7  mmm). 
Nerve  cells  vary  from  ^i^  toxoioo  of  an  inch  (83.5  to  2.5 
mmm;  muscular  fibre  cells  Tfy'jnr  to  -^rhr^  of  an  inch,  (5.5  to 
10  mmm.)  in  diameter.  The  cell  may  be  divided  into  a  cell 
wall,  nucleus,  nucleolus  and  contents. 

Cell  Wall. — The  cell  wall,  when  present,  is  substan- 
tially the  same  in  all  cells,  and  is  formed  by  the  consolida- 


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PRIMARY  h\  RMS  OF  TISSUE. 


49 


tion  of  the  outer  surface  of  tlio  mass  of  protoplasm.  It  is 
a  simple  homogeneous  membrane,  composed  oi  globuline, 
and  although  no  pores  can  be  seen  by  the  highest  magnify- 
ing power,  yet  it  possesses  the  property  of  osmosis.  In 
some  instances  it  is  extremely  thin ;  in  others  dense  and 
unyielding.  When  the  cell-wall  is  acted  on  by  acetic  acid, 
it  swells  out  and  becomes  transparent,  so  as  to  bring  into 
view  the  nucleus,  when  that  body  exists. 

Nucleus. — In  the  interior  of  most  animal  cells  is  seen 
a  small  body,  which  is  called  the  nuckus.  It  exists  either 
in  the  form  of  a  small  vesicle,  or  as  a  small  mass  of  proto- 
plasm, containing  one  or  more  minute  particles  termed 
nucleoli.  The  nucleus  is  generally  situated  in  or  near  the 
centre  of  the  cell,  but  may  be  attached  to  the  wall,  or 
imbedded  in  it,  as  in  the  fat  cell.  It  is  generally  rounded 
in  form,  but  may  be  found  elongated,  as  in  the  nonstriated 
muscular  fibre  cell.  The  size  of  the  nucleus  varies  from 
Tir'oTs  to  oT,V()  of  an  inch  (6  to  4  mmm.)  in  diameter.  It  is 
more  regular,  both  in  shape  and  size,  than  the  cell  itself. 
In  most  instances  each  cell  contains  but  one  nucleus  ; 
cartilage  cells  frequently  contain  two  or  more.  When  two 
or  more  nuclei  are  found  in  one  cell,  it  is  generally  an 
evidence  of  rapid  growth,  as  in  fibro-cellular  tumors, 
cancer,  pus,  etc.  In  giant  cells  there  may  be  a  multitude 
of  nuclei  in  each  cell  (Fig.  14  e.).  They  are,  in  these 
cases,  formed  by  the  subdivision  of  the  original  nucleus. 

The  nucleus  resists  the  action  of  acids  and  alkalies 
better  than  any  other  part  of  the  cell.  It  is  readiiy 
stained  by  ammoniacal  solution  of  carmine,  and  hence 
is  regarded  by  Beale  as  gevminal  ^matter  in  contra- 
distinction to  the  outer  portion  of  the  cell,  which  he  calls 
formed  matter. 

Nuclei  are  sometimes  found  disconnected  from  the  cells, 
when  they  are  said  to  be  free.  They  may  be  found  floating 
in  fluid  as  in  certain  secretions,  or  imbedded  in  a  homogen- 
eous pellucid  substance,  as  in  rudimental  cellular  tissue,  or 


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PRIMARY  FORMS  OF  TISSUE. 


on  tho  surface  of  fibres,  as  in  muscle  and  nerve  fibres,  in 
which  they  are  either  upon  or  inunediately  beneath  the 
investing  membrane.  The  nucleus  is  a  most  persistent  little 
body,  and  retains  its  original  form  in  many  cases  after  the 
cell  to  which  it  belongs  has  ceased  to  exist  as  such. 

Nucleolus. — This  is  situated. in  the  interior  of  the  nu- 
cleus, and  may  consist  of  a  single  molecule,  or  a  number 
united  together.  In  some  instances  it  is  highly  refracting, 
and  not  readily  acted  upon  by  most  chemical  re-agents. 
There  may  be  one  or  more  in  each  cell. 

Contents. — The  contents  of  all  cells  consist  of  a  certain 
amount  of  protoplasm  mingled  with  other  substances. 
Each  cell  has  the  power  of  generating  in  its  interior  a  sub- 
stance peculiar  to  itself,  which  is  the  result  of  its  own  se- 
cretion ;  one  secretes  bile,  another  milk,  another  mucus, 
another  gastric  juice,  etc.  The  contents  of  the  cell  may  be 
either  solid,  as  in  bone,  nails,  epidermis,  etc.,  or  fluid,  as  in 
blood,  chyle,  mucus,  etc.  The  contents  of  all  cells  are  fluid 
when  formed,  but  become  hardened  by  secondary  deposit, 
as  in  bone,  dentine,  etc.  This  takes  place  by  the  deposition 
of  solid  particles  in  the  interior  of  the  cell.' 

Color. — Cells  are  generally  colorless  ;  a  few  only  have 
color  which  depends  partly  on  their  refracting  power,  and 
partly  on  the  hemoglobine,  melanine,  or  pigment  which  they 
contain,  as  the  red  blood  corpuscles,  pigment  cells,  etc. 

Protoplasm,  or  Cijtohlastema. — This  is  the  name  given 
to  the  substance  from  which  the  cells  spring,  and  is  derived 
either  from  the  fluid  in  which  they  float,  as  blood, 
chyle,  lymph;  or  from  the  capillaries  near  the  seat  of  growth. 
When  the  cells  are  situated  on  a  basement  membrane,  as 
the  epithelium  of  mucous  and  serous  membranes,  it  is  found 
surrounding  them,  having  passed  through  the  basement 
membrane  from  the  capillaries  immediately  beneath.  In  all 
these  cases  the  cytoblastema  contains  material  not  only  to 
supply  the  wants  of  the  present  brood  of  cells,  but  also  for 
the  development  of  the  new  brood  which  is  destined  to  take 
the  place  of  the  old. 


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PRIMARY  FORMS  OF  TISSUE. 


51 


Tliocoll  has  alno  tho  power  of  choosinjj  and  ret'u.siii*j  from 
the  particles  of  nutrient  fluid  or  cytohhisteina  in  its  neigh- 
bourliood,  incorporating  some  of  them  into  its  substance, 
and  converting  others  into  new  substances  in  its  interior. 
For  example,  the  blood  cori)usele  has  the  power  of  forming 
globuline  and  hemoglobine  from  the  albumen  and  fibrin  of 
the  blood.  It  is  Cv^iitended  by  some  physiologists  that  this 
power  resides  solely  in  the  nucleus ;  but  it  must  be  borne 
in  mind  that  this  property  belongs  alsc  to  those  cells  which 
are  entirely  destitute  of  a  nucleus,  as  the  blood  corpuscle, 
germ  cells  of  the  vegetable  kingdom,  etc. 

Cytooenesis.  —  KwTor  "cell"  and  '^iitui  "generation." 
evils  have  their  j^eriod  of  birth, growth, maturity,aud decline. 
They  spiiug  up,  ])erform  their  ottice,  and  then  pass  away. 
Some  do  so  witli  great  rapidity,  while  others  are  slower  in 
their  progress,  or  are  longer  lived.  They  are  governed  by 
certain  laws,  two  of  which  we  may  here  formulate. 

Xst  Law. — In  all  tissues  composed  of  cells,  the  new  cells 
which  are  being  developed  must  resemble  the  ]jarent  cells  in 
all  their  distinctive  features  and  properties.  When  the 
young  cell  deviates  in  its  character  from  the  parent  cell, 
abnormal  growth  may  be  said  to  have  commenced. 

^nd  Law. — Cell  growth  can  only  take  place  in  or  near 
its  appropriate  pabulum,  and  on  living  surfaces. 

The  mode  of  origin  of  cells  takes  place  in  several  ways. 
Schleiden  and  Schwann,  as  far  back  as  1838,  asserted  that 
cells  were  developed  de  novo  in  an  organizable  blastema. 
According  to  this  theory  the  cell  was  developed  by  the  foi-- 
matiou  of  granules  in  the  blastema,  their  subsecjuent  ar- 
rangement to  form  the  nucleolus,  around  which  at  a  certain 
distance  was  formed  the  nucleus,  and  lastly  the  cell  wall 
and  contents  ;  or  the  order  might  be  reversed  by  the  for- 
mation, first  of  the  cell  wall,  and  subse(iuently  the  nucleus 
and  nucleolus.  This  theory  oi  free  cell  formation  still  has 
its  advocates  among  many  French  physiologists,  especially 
Robin. 


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52 


PKIMAKV  FORMS  OP   TISSUE. 


According  to  the  modern  doctrine,  which  was  first  advo- 
cated by  Virchow  in  1852,  every  cell  must  originate  from  a 
pre-existing  or  parent  cell  {omnis  cellula  e  cellula.)  There 
are  three  difi'erent  modes  by  which  cells  may  bo  produced 
in  this  way. 

1st.  By  Midfi plication  by  suh-divif^ion,^ss\on,  orfis.sip- 
arous  multiplication  of  the  cell.  This  process  has  been  seen 
in  the  anui4)a,  and  in  the  blood  corpuscles  of  the  lower 
animals.  The  cartilage  coll  also  fmnishes  a  good  example. 
The  cell  is  originally  rounded ;  but  when  the  process  of 
subdivision  commences,  it  becomos  oval,  and  subsequently 
]>resents  a  sort  of  hour-glass  contiaction,  first  of  the  nu- 
cleus, and  afterwards  of  the  cell.  This  continues  until 
Fiji.  17.  there  is  a  complete  separ- 

ation, first  of  the  nucleus 
i  uto  two  parts,  and  then  the 
cell,  each  ]iart  of  the  nu- 
cleus drawing  a  })ortion  of 
the  coll  or  cell- wall  around 
it.     This  process  may  be 

A  ifll  midoi'Ljoiiij;' till"  lUMfoss  of  multiiilioiitioii  .  •.        .  , 

i.y  siiii.iiviMoii.    ^iO  ()n,i;inai  ivii.    (1.)  Oval,  agaiu    repeated    in    each 

(c)— Uinir-j;liis»  ooiitnu'tion   and   division   of    tlie  .    ,  .  ., 

tiucii'ii!,.  ^d)  Division  of  the  loii  into  two.  y)art,  Cither  lu   tliG  .sauio 

direction  or  transversely,  so  as  to  form  four  now  cells,  and 
so  on  until  a  number  have  been  produced.  This  is  the 
mode  by  which  segmentation  of  the  vitellus  takes  place. 

2nd.  By  subdivision  of  the  nucleus  or  contents  of  the 
cell  only,  the  so-called  ondojjfonous  mode.     In  this  mode  the 
'  '^  '^  nucleus  a[)pears  to  sc})arate  into  two  or  mora 

parts,  each  of  which  is  developed  into  a  new 
coll,  and  in  this  way  the  parent  cell  may  be 
filled  by  a  wb.olo  brood  of  young  cells,  the  so- 

This  variety  of  cell 

development  may  be  observed  in  bone  cells,  (Frey)  also  m 

structures   of  very  rapid  growth,  as   in  cancerous   tissue. 

3rd.  By  gemmation  or  budding.     In  this  case  a  node  or 

swelling  is  setu  on  one  side  of  the  cell  which  gradually  in- 


A  cell  containing  a  called  daughter  cells, 

number  of  joung  oells.  o 


PRIMARY  FORMS  OP    TISSUE.  $5 

creasing,  finally  drops  off  by  constriction  at  the  base.  The 
yeast  cell  is  propagated  in  tliis  manner. 

Dr.  Bealo  accepts  the  modern  doctrine,  and  the  term  "pro- 
toplasm "  as  the  substance  from  which  cells  are  formed, 
but  makes  a  distinction  between  the  nucleus,  which  is 
readily  stained  with  carmine,  and  the  rest  of  the  cell.  Ho 
terms  the  nucleus  "  germinal  "  or  living  matter,  in  contra- 
distinction to  the  outer  ])ortions  of  the  cell,  which  he  calls 
"formed  matter,"  designating  by  the  latter,  the  various  tis- 
sues formed  from  cells. 

Conditions  nkckssar\  to  Ckll  Gkowth. — The  condi-  C! 

tions  necessary  to  cell  growth  are  the  pjesonce  of  protoplasm  C 

upon  a  living  surface,  a  certain  degree  of  animal  licat,  a  re-  S^ 

quisite  amount  of  water,  oxygen,  light  and  electricity.     The  |, 

dynamic  agency  of  heat  cannot  be  dispensed  with  ;  too  juiich  r* 

would  be  injurious.  The  mysterious  iulluence  of  light  is 
necessary  to  healthy  action,  and  a  certain  amount  of  water 
is  required  to  preserve  the  integrity  and  piomote  the  growtli  ■  'J 

of  the  cell;  but  too  much  would  destroy  it.  <S  1 

Permanent  Change  in  the  shape  of  Cells. — Cells  un-  ^.^  J 

dei'go  changes  in  the  formation  of  tissues,  and  in  the  ])ro-  |  j 


c 


•iOr 


pagation  of  their  kind,  by  which  they  lose  their  individuality 

as  cells,     This  may  be  seen  :  jt 

1st.  By  the  process  of  cytogenesis,  as  in  multiplication  by  %-. 

sub-division  etc.,  which  has  already  been  described.  gj 

2nd.  By  coalescence  of  the  cell  with  tlie  intercollular  sub-  2i 

stance  of  temporary  cartilage,  as  in   the    development   of 
osseous  tissue.     (See  development  of  bone.) 

3rd.  By  the  coalescence  of  cells,  with  tlie  intercellular 
substance  to  form  fibres  as  in  fibrous  tissue.  The  cells  aie 
originally  round  ;  but  in  the  process  of  fonning  fibres  they 
become  elongated,  and  in  some  instances  fusiform  or  stellate. 
They  are  then  arrang(id  hingitudinally,  sometimes  slightly 
overlapping  each  other,  and  both  the  cells  and  the  inter- 
cellular substance  are  broken  uj)  into  fibrilhe. 

4th.  By  the  coalescence  of  cells  in  a  linear  manner  to  form 
tubes.      In  this  instance  the  opposing  walls  of  the  cells,  as 


54 


PRIMARY  FORMS  OF    TISSUE. 


m 


they  are  arranged  in  a  line,  break  down,  the  cavities  of  the 
cells  communicate  with  each  other,  and  in  this  way  a  con- 
tinuous tube  is  formed,as  in  the  developmer),t  of  muscular  and 
nerve  fibres,  also  in  the  formation  of  small  vessels ;  or  the 
cells  may  assume  the  form  of  curved  plates  or  segments, 
united  or  cemented  together  in  such  a  way  as  to  form  a  tube. 

Temporary  Change  in  the  Shape  of  Cells. — Tem- 
porary changes  in  the  shape  of  cells  give  rise  to  motion. 
Tlie  cause  of  motion  in  the  vegetable  kingdom  was  for  a  long 
time  a  matter  of  speculation.  It  was  finally  discovered 
that  this  phenomenon  was  due  to  the  change  in  the  shape 
of  the  cells  when  irritated,  as  in  the  mimosa  or  sensitive 
plant,  the  fly-trap  of  the  dionoea,  and  the  berberis. 

In  the  animal  economy,  muscular  contraction  is  due  to 
this  temporary  change.  It  occurs  in  both  the  striated  and 
non-striated  muscular  tissue.  In  contraction  of  the  fibrillai 
the  sarcous  elements  become  shorter  and  broader  ;  the  same 
is  true  of  the  non-striated  muscular  fibre  cells.  Temporary 
changes  in  the  shape  of  the  cells  take  place  in  the  uterus, 
during  gestation.  The  cells  are  largely  developed  during 
pregnancy,  in  order  to  give  enlarged  accommodation  for  the 
foetus,  and  increased  power  for  the  act  of  parturition. 
After  birth  the  uterus  undergoes  the  process  of  involution, 
by  which  the  cells  are  diminished  in  size  and  number,  and 
changed  in  their  physical  appearance.  When  examined  by 
the  miscroscope,  oil  globules  may  be  seen  in  their  interior 
at  this  stage.     (Fig.  10.) 

In  some  instances  the  change  in  the  shape 
of  the  cell  appears  to  be  entirely  of  a  spon- 
taneous character,  as  in  the  amoeba  and  white 
corj»uscles  of  the  blood,  in  both  of  which, 
changes  in  shape  are  constantly  occurring  at 
certiiiu  periods,  and  under  certain  circum- 
stances. 

AMfKBA.        Ill     the  f.        I  .,.  „  •    1       l«     1 

centre  is  seen  the      Uie  movcmcnts  01  the  Cilia  of    epithelial 

nucleus,     and    sur-  .  i  i  i  i 

rounding  it  a  nuni-  cells  are  110  doubt  also  produccd  by  the  spon- 

niber  of  vacuoles.  *■  . 

taneous  change  in  the  sha])e  of  the  cells  from  which  they 


Fijr.     19. 


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PRIMARY  FORMS  OF  TISSUE. 


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spring, 


These  movements  are  probably  caused  by  the 
alternate  contraction  and  relaxation  of  the  cells,  and  also  of 
the  cilia. 

Cause  of  Organization,  Vitality,  &c. — This  is  a  purely 
speculative  subject.     Many  theories  have  been  advanced 
from  time  to  time,  to  endeavor  to  explain   the  phenomena 
of  organized  bodies.     Some  suppose  that  organization  is 
due  to  an  "  animating  principle  "   which  pervades  every 
organized   structure    and    regulates   its  functions,  and  by 
which  the  new  organism  for  the  production  of  the  species 
is  moulded  into   shape,  from  materials  fuinished  by  the 
parent.     This  was  the  theory  of  Aristotle,  and  was  after- 
wards advocated  by  Harvey.    Hunter  attributed  the  organi- 
zation of  living  beings,  and  the  vital  action  manifested  by 
them,  to  a  "  materia  vittie  "  diffused  throughout  the  solids 
and  fluids  of  the  body.     Abernethy  supposed  this  matei'ia 
vitjB  to  be  of  a  species  of  electricity.     Milller  supposed  that 
the  cause  of  organization  was  due  to  an   "  organic  force  " 
which  resides  in  the  whole  organism,  and  possesses  the 
property  of  generating  each  part.     This  "  organic  force  " 
exists  already  in  the  germ,  and  is  creative,  as  is  seen  in  the 
production  and  ari-angement  of  cells  to  form  the  different 
parts  of  the  new  organism.     It  is  not  under  the  influence 
of  the  mind,  as  instinct  is  as  capable  of  reproducing  the 
species  as  higher  intelligence.     Prout  advocated  the  exist- 
ence of  an   "  organic  agent,"  which  possesses  extraordinary 
powers  in  controlling  and  directing  the  organization  and 
development  of  the  living  being.     This  is  very  similar  to 
the  preceding  hypothesis. 

There  can  be  no  doubt,  however,  that  organic  matter  de- 
rives its  vital  properties  from  a  previously  existing  vital 
organism.  While  these  organic  matters  retain  a  perfect 
organization,  and  are  supplied  with  their  proper  stimuli,  as 
light,  heat,  moisture,  etc,  vital  actions  go  on  perfectly  :  for 
example,  the  fecundated  Qgg,  "omne  vivum  ex  ovo,"  accpiires 
its  vital  properties  while  in  the  body  of  the  mother ;  and 


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56 


PRIMARY  FORMS  OF  TISSUE. 


when  laid,  if  supplied  with  the  vital  stimuli,  and  the  organiza- 
tion remain  perfect,  it  is  developed  into  a  new  being.  But 
as  soon  as  the  structure  is  destroyed,  or  the  vital  stimuli  are 
withheld  or  withdrawn,  the  organism  dies,  and  its  elements 
form  new  compounds,  most  of  which  are  of  an  inorganic 
character. 

Function  of  Cells. — The  function  of  cells  is  exhibited 
in  the  plastic  and  metabolic,  or  vital  and  chemico-vital 
power  of  the  cell.  The  plastic  power  of  the  cell  is  seen  in 
its  development  from  protoplasm;  the  proliferation,  by  multi- 
plication of  new  cells,  their  subsequent  growth  and  de- 
velopment, and  their  transformation  in  the  development  of 
the  tissues  of  the  body. 

The  metabolic  or  chemico-vital  power  of  the  cell  is  shown 
in  the  property  it  has  of  chemically  changing  the  protoplasm 
within  and  without  tlie  cell.  It  is  confined  to  the  conver- 
sion of  special  substances,  as  in  the  formation  of  globuline 
and  hemoglobine,  by  the  blood  corpuscle,  bile  by  the  hepatic 
cell,  and  pepsine  by  the  gland  cells  of  the  stomach,  etc.  The 
cell  of  the  yeast  plant  has  also  the  power  of  converting 
sugar  into  alcohol  and  carbonic  acid.  These  two  forces 
(plastic  and  metabolic)  may  act  together  :  in  fact,  it  is  diffi- 
cult to  separate  them,  for  while  the  cell  is  growing  it  is 
already  beginning  to  perform  its  office.  Both  these  forces 
act  together  in  harmony,  and  through  their  united  action 
the  different  secretions  and  excretions  are  formed.  They 
are  affected  by  nervous  impressions,  as  fear,  joy,  grief, 
anger,  etc.  For  example,  the  character  of  the  milk  is 
changed  by  a  fit  of  anger,  and  the  secretion  of  the  gastric 
juice  is  arrested  by  fear. 

The  plastic  and  metabolic  power  of  the  cell  may  be 
arrested  by  powerful  chemical  re-agents,  as  arsenic,  corro- 
sive sublimate,  acids  and  alkalies.  It  is  also  arrested  by 
strong  nervous  shocks,  as  a  stroke  of  lightning,  or  a  powerful 
battery,  and  by  septic  poisons.  The  function  of  the  cell  is 
also  further  manifested  in  the  permanent  change  it  under- 
goes in  the  formation  of  tissues  already  described. 


PRIMARY  FORMS  OF  TISSUE.  57 

Manifestations  of  Cell  Life. — These  are  exhibited  : 

First — In  cell  growth  from  protoplasm. 

Second — In  the  multiplication  or  production  of  new  cells 

Third — In  the  chemico-vital  transformation  of  protoplasm 

Fourth — In  the  permanent  change  in  the  cell. 

Fifth — In  the  temporary  change  in  th'e  cell. 

Sixth — In  the  production  of  nervous  force  (vis  nervosa.) 

A  cell  is  a  living  organism,  and  like  all  living  bodies,  has 
its  period  of  growth,  maturity  and  decay.  It  has  the  power 
of  selecting  matters  from  the  nutrient  elements,  assimilating 

and  organizing  them  into  new  substances  found  in  its  inte-  ^ 

rior.     This  property  resides  in  the  cell  as  a  whole,  and  not  ^ 

exclusively  in  any  single  part  of  it.      The  duration  of  the  fj^ 

life  of  a  cell  depends  on  its  activity  ;  those  of  slow  develop-  |« 

ment  are  long-lived,  and  vice  versa.  When  a  cell  begins  to 
decay,  gi-anular  matter  is  first  noticed  in  its  interior ;  the 
cell  wall  or  outer  portion  dissolves,  and  the  cell  finally 
disappears.  E, 

GRANULES. 


m 


C  ' 


ftktf. 


-.1 


Granules  or  molecules  are  minute  particles  of    matter  »*  ] 

from  T^lijo^  to  jYwi)S  of  ^^  ^^^^  (^-^  to  1  mmm)  in  diameter.  I,  ■' 

Some  appear  as  dark  specks,  while  others  present  a  dark  ^ 

outline  with  a  bright  centre;  this  latter  is  characteristic  of  f^. 

fat    globules.      They   may   be   found   incessantly   moving  *•;* 

about  in  the  interior  of  cells,  or  in  the  fluids,  as  the  granules  uV 

of    pigment   cells,  called   [)igment   granules.      They   may  « 

exist  either  in  the  free  state,  as  in  chyle,  milk,  blood  etc. ;  in- 
closed in  cells,  or  imbedded  in  the  tissues  as  in  bone,  den- 
tine, cartilage.  They  are  present  in  great  abundance  in  chyle 
and  give  .o  that  fluid  its  opalescent  appearance  (Fig.  7.) 
The  molecules  of  chyle  are  of  low  specific  gravity,  readily 
soluble  in  ether,  and  are  known  as  fat  globules  or  granules. 

SIMPLE   FIBRES. 

A  simple  fibre  is  formed  by  the  arrangement  and  coal- 
escence of  granules  or  molecules  in  a  linear  manner.     They 


it-iiiV, 


ii 


58 


PRIMARY  FORMS  OF   TISSUE, 


vary  in  size  from  jirJinT  ^o  TDonir  of  an  inch  (2.5  to  1.25  mmm.) 
in  diameter,  and  are  rounded  or  prismatic  in  shape  depend- 
ing on  pressure.  Tliey  are  formed  in  the  coagulation  or 
fibrillation  of  filain,  and  they  constitute  the  primitive 
fibrillse  of  striated  muscular  tissue.  As  coagulation  of  the 
fibrin  takes  i)lace,  star-shaped  points  are  first  formed,  and 
the  granules  arran^je  thonuselves  in  a  linear  manner  from  one 
point  to  another  and  coalesce  to  form  fibi-es,  until  the  process 
is  completed  (Fig.  13.)  This  was  formerly  believed  to  be  the 
mode  of  healing  or  organization  in  woundsandadhesive  bands 
in  inflammation,  from  the  coagulable  lymph  or  fibrin  which 
was  exuded  from  the  blood-vessels  for  that  purpose.  The 
modein  view  regarding  this  subject,  is  that  "  coagulable 
lymph  "  is  the  product  of  the  white  corpuscles,  which 
have  passed  through  the  coats  of  the  vessels  by  virtue  of 
their  amoeboid  movements,  supplemented  by  the  prolifera- 
tion of  the  connective  tissue  cells  in  the  wounded  or  inflamed 
parts. 


SIMPLE  OR   BASEMEIST  MEMHRANES. 

These  are  formed  directly  from  the  nutrient  fluid  or 
protoplasm,  by  a  certain  arrangement  of  molecules  peculiar 
to  themselves.  They  are  found  in  the  walls  of  most  cells, 
in  the  sarcolemma  of  muscular  fibre,  in  the  sheath  of  nerve 
fibre,  in  the  covermg  of  the  vitreous  humor,  in  the  vitelline 
membrane  of  the  ovum,  and  as  the  structure  upon  which 
the  epithelium  rests  in  membranous  expansions.  They  exist 
under  three  different  forms,  which  vary  somewhat  in  micro- 
scopical appearance. 

In  iVajirst  variety,  it  is  a  simple  pellicle  of  homogeneous 
appearance,  and  shows  no  sign  of  organization,  as  in  the 
cell  wall.  A  good  example  may  be  seen  in  the  lining 
membrane  of  a  bivalve  shell.  In  the  second  variety,  the 
membrane  presents  a  number  of  minute  granules  irregularly 
scattered  through  the  transparent  substance.  In  the  third 
variety,  the  membrane  presents  a  numl    r  of  distinct  spots 


PRIMARY  FORMS  OF  TISSUE. 


59 


or  nuclei,  and  is  capable  of  being  torn  up  into  portions  of 
nearly  equal  size,  each  containing  one  of  these  spots  or 
nuclei.  From  this  it  wduld  appear  that  the  jirst  variety  is 
formed  by  the  condensation  of  a  thin  layer  of  protoplasm, 
the  second  by  the  condensation  of  a  thin  layer  of  protoplasm 
in  which  granules  had  been  formed,  and  the  third  by  the 
condensation  of  a  thin  layer  of  protoplasm  in  which  nuclei 
had  been  formed. 

Certain  forms  of  membrane  above  described  have  been 
called  by  some  basement  membranes,  because  they  are  the 
foundation  or  resting  place  for  the  epithelial  cells  ;  by 
others,  primary ,  germinal,  or  maternal  memV>ranes,  because 
they  furnish  the  germs  of  these  cells.  They  are  also  called 
hyaline.membranes,  because  of  theirstructureless  appearance. 
Basement  membrane  is  found  on  all  the  free  surfaces  of  the 
body,  giving  support  to  the  epithelial  cells.  It  forms  the 
outer  layer  of  the  true  skin,  and  the  inner  layer  of  mucous 
serous  and  synovial  membranes,  blood-vessels  and  lym- 
phatics. It  is  also  prolonged  into  ali  th?  ducts,  follicles 
and  tubuli  connected  with  the  mucous  membranes.  In  all 
these  examples  its  free  surface  is  covered  with  cells,  which 
receive  their  nutriment  by  osmosis,  through  the  membrane, 
from  the  capillaries  on  its  attached  surface.  Its  office  is  to 
limit  osmosis  of  the  nutrient  fluid,  and  to  modify  it  in  its 
passage.  It  also  supports  the  cells,  and  probably  determines 
the  formation  of  all  the  cells  which  are  developed  on  its 
surface.  In  all  probability,  the  spots,  or  nuclei,  seen  in  the 
basement  membrane  are  the  germs  of  cells,  which  spring 
from  them  as  from  a  centre. 


r 
c 

c 
I. 

I- 

m 

m\ 


J 

■  ( 

I 


CO 


TISSUES. 


CHAPTER  III. 


TISSUES. 


There  are  seven  distinct  tissues  in  the  body  viz  :  white 
fibrous  or  connective,  yellow  elastic,  adipose,  cartilage,  bone 
(including  dentine  and  enamel),  muscle  and  nerve  tissue,  to 
which  may  be  added  gelatinous  tissue  and  reticular  con- 
nective tissue  of  modern  histologists.  All  other  tissues  are 
made  up  of  a  combination  of  two  or  more  of  these.  All,  ex- 
cept muscular  and  nerve  tissues  are  considered  by  some  to 
be  modified  forms  of  connective  tissue,  and  are  described  as 
the  connective  tissue  group. 

WHITE   FIBROUS,  OR  CONNECTIVE  TISSUE. 

This  tissue  enters  into  the  formation  of  ligaments,  tendons 
aponeuroses  and  membranes. 

1st.  As  ligaments,  it  connects  the  bones  together  and  pre- 
serves the  integrity  of  the  joints  in  their  various  move- 
ments. The  ligaments  assume  three  different  forms  :  Fu- 
nicular, which  consists  of  rounded  cords  of  fibrous  tissue, 
as  the  ligamentum  teres.  Fascicular,  which  consists  of 
flattened  bands,  as  the  ligaments  of  the  ankle,  knee,  and 
elbow  ;  and  Capsular,  which  forms  tubular  expansions,  as  in 
the  shoulder  and  hip  joints. 

2nd.  As  tendons,  it  serves  to  connect  the  muscles  to  the 
bones  and  other  structures  to  which  they  are  occasionally 
attached  ;  some  of  these  are  round — Funicular,  as  the  ten- 
don of  the  semi-tendinosus  ;  others  flattened — Fascicular,  as 
the  semi-membranosus.  The  tendons,  at  their  insertion  in- 
to the  bones,  blend  with  the  periosteum. 

3rd.  As  aponeuroses.  These  are  tendinous  expansions  of 
considerable  extent,  as  in  the  abdominal  muscles.  They 
serve  to  enclose  cavities,  and  protect  the  contained  organs. 


4 
vari 
peri 
driu 
are 

P 
beai 
neoi 
whi 
inte 
foun 
mm 
ous 


Com 
(b)Elt 
deoli, 

(1.6 
rate( 


CONNECTIVE  TISSUE. 


61 


^th.  As  memhranes,  it  is  used  to  cover,  protect,  and  attach 
various  organs,  as  the  dura  mater,  sclerotic  coat  of  the  eye, 
pericardium,  tunica  albuginea  testis,  periosteum,  perichon- 
drium, fascia  lata,  &,c.  In  all  the  above,  a  few  elastic  fibres 
are  found  associated  with  the'white  fibres. 

Physical  Appearance  and  Properties. — It  presents  a 
beautiful,  silvery- white  appearance,  when  freed  from  extra- 
neous substances,  and  is  composed  of  bundles  of  fibres, 
which  are  parallel  to  each  other  in  some  cases,  and  cross  or 
interlace  in  others.  Exa  'ned  under  the  microscope,  it  is 
found  to  consist  of  wavy  bands  about  too  of  an  inch  (50 
mmm)  in  diameter  (Fig  20,  a.)  They  are  formed  of  numer- 
ous fibrillse,  varying  in  size  from  irlinr  to  tehji^  of  an  inch 

Fig.  20. 


Connective  and  elastic  fibres,  (a)  Connective  fibres,  having  some  embryo.  Ac  crlobules* 
(b)  Elai^tic  fibres,  (c)  Curly  elastic  fibres,  like  horse  hair.  (d)  Nuclei  of  cells,  with  nu- 
cleoli, X  820.     (Todd  and  Buwman.) 

(1.6  to  1.2  mmm.)     The  bands  are, capable  of  being  sepa- 
rated into  fibrillae,  and  have  a  tendency  to  split  up  in  a 


r 
c 

c 
I. 

I* 


r 

w 

tni    . 


t 

A 

1 

It 

» 

I 


62 


TISSUES. 


longitudinal  direction.  When  a  portion  is  exposed  to  the 
action  of  acetic  acid,  it  swells  out  and  becomes  semi-trans- 
parent, the  fibrilhc  are  entirely  obliterated,  and  a  number  of 
connective  tissue  corpuscles  make  their  appearance,  showing 
that  it  has  been  developed  from  cells.  At  the  same  time 
some  wavy  transverse  lines  may  be  seen  at  regular  distances, 
which  somewhat  resemble  striped  muscular  fibre.  These 
lines  mark  the  junction  or  outline  of  the  cells  from  which 
the  tissue  was  originally  formed.  A  number  of  wandering 
cells  (white  corpuscles)  and  connective  tissue  corpuscles,  are 
always  found  in  connection  with  fibrous  tissue.  This  tissue 
is  somewhat  elastic,  and  allows  of  a  slight  degree  of  exten- 
sion from  long-continued  force.  It  possesses  no  contractility, 
and  its  force  of  cohesion  is  very  great.  It  is  said  that  the 
tendo-achillis  is  capable  of  supporting  a  weight  of  nearly 
1,000  lbs.  It  contains  few  vessels  and  nerves.  The  actual 
presence  of  nerves  has  not,  as  yet,  been  satisfactorily  demon- 
strated, and  its  sensibility  is  very  low.  The  division  of  a 
tendon  is  attended  with  very  little  pain.  It  yields  gelatine, on 
boiling. 

YELLOW  FIBROUS,  OR   ELASTIC   TISSUE. 

It  is -found  in  the  ligamenta  subflava,  ligamentum  nuchte 
of  quadrupeds,  internal  lateral  ligament  of  the  lower  jaw, 
stylo-hyoid  and  pterygo-maxillary  ligaments,  chorda3  vo- 
cales,  crico- thyroid  and  thyro-hyoid  membranes,  posterior 
wall  of  the  trachea,  arteries,  veins,  thoracic  duct,  and  in 
areolar  tissue. 

Physical  Appearance  and  Properties. — This  tissue,  un- 
like the  preceding,  is  of  a  yellowish  color,  highly  elastic  and 
consists  of  long,  single,  brittle  fibres,  with  sharply  defined 
dark  borders,  which  show  a  disposition  to  curl  upon  themsel- 
ves when  broken  (Fig.  20,  b).  They  vary  in  size  from  ^oVw  to 
T50GO  of  aii  inch  (5.  to  2.5  mmm.)  the  average  diameter 
being  about  y^\^^  of  an  inch  (3.5  mmm.)  and  are  round  or 
flattened — depending  oij  their  situation  or  pressure.     They 


ana! 
por 
sue. 


ELASTIC  TISSUE. 


(J3 


anastomose  with  each  other,  and  are  mingleil  in  varioiis  pro- 
portions witli  tlio  white,  to  form  areolar  or  connective  tis- 
sue. It  yields  a  modified  form  of  gelatine  on  prolonged  boil- 
ing; is  not  acted  on  by  acetic  acid,  and  is  not  readily  dissolved 
by  the  gastric  juice.  The  fibres  are  stained  red,  with  Millon's 
re-agent  (a  solution  of  proto,  and  pernitrate  of  mercury). 
It  resists  the  approach  of  disease  longer  than  any  other  tis- 
sue in  the  body ;  e.  <;.,  an  artery  will  remain  intact  in  the 
interior  of  an  abscess  after  the  other  structures  are  destroyed, 
and  when  the  artery  gives  way,  the  walls  present  a  honey- 
combed appearance.on  account  of  the  destruction  of  the  white 
fibrous  and  muscular  tissues  with  which  it  is  associated. 
When  dried  it  becomes  dark  colored,  hard  and  loses  its 
elasticity.  It  is  sparingly  supplied  with  blood  vessels  and 
nerves.  The  fibres  are  marked  by  transverse  lines,  in  the 
lower  animals,  which  shows  that  it  is  developed  from  cells. 
Its  elasticity  is  impaired  by  age. 

Mode  of  Development. — This  is  now  believed  to  be  the 
same  in  both  connective  and  elastic  tissue.  They  were  sup- 
posed by  Heul5  to  be  developed  V)y  the  process  of  fibrillation. 
Their  real  mode  of  growth  was  first  pointed  out  by  Schwann, 
to  be  from  cells.  The  cells  are  at  first  round,  and  possess  a 
nucleus,  nucleolus  and  granular  matter.  They  then  become 
fusiform,  or  stellate,  surrounded  by  intercellular  substance, 
and  being  applied  or  spliced  in  a  linear  manner,  coalescence 
takes  place,and  fibrillse  are  formed  (Fig.21).  At  the  same  time 
the  nuclei  become  elongated,  and  finally  ^''^-  ^^• 

disappear,  until  brought  into  view  by 
means  of  acetic  acid.  According  to 
late  observers  a  certain  amount  of 
material  is  formed  by  the  cells,  called 
iissite  cement  or  intercellular  sub- 
stance, in  which  the  cells  become  im- 
bedded, and  which  serves  to  unite 
them  together.  This  substance 
blackened  by  nitrate  of  silver  (Frey)  ^i^p-^ -»«•  (b). -ar^eBrauuiar 


c 
c 

r 
I. 
1^ 

»; 

m\ 
I 

c 

r 


1 
I 


►  *-, 
»» 

mi 


Cells  of  human  connective  tis- 
IS  sue.    (a),  flat  stellate  or  shovel- 


64 


T/SSl/ES. 


Arkolar  Tissue,  (Syn„  cellular,  connective  or  filamen- 
tous.) This  tissue  is  found  in  all  parts  of  the  body  except 
the  brain,  compact  tissue  of  bone,  teeth,  cartilage,  hair, 
nails,  epidermis,  etc.  It  consists  of  a  network  formed  by  a 
combination  of  white  fibrous  or  connective  tissue  and  yellow 
elastic  tissue,  together  with  a  number  of  connective  tissue  cor- 
puscles. Where  great  strength  is  required,  the  connective 
tissue  predominates,  and  where  motion  is  necer..sary,  the 
elastic,  as  in  the  tit'sue  of  the  lungs.  The  proportion  of 
each  may  be  easily  demonstrated  by  acting  on  it  with  acetic 
acid,  whljh  dissolves  out  the  whitp,  while  it  produces  no 
change  on  the  yellow.  The  interstices  or  meshes  (impro- 
perly called  cells)  of  areolar  tissue  communicate  with  each 
other.  This  tissue,  therefore,  may  be  inflated  with  air  (the 
butchers  take  advantage  of  this  circumstance  in  inflating 
their  meat),  or  the  meshes  may  be  filled  with  fluid,  as  in 
anasarca.  The  interstices,  especially  in  the  subcutaneous 
areolar  tissue,  are  partially  filled  with  fat  cells,  and  contain 
a  small  quantity  of  serous  fluid  of  an  alkaline  reaction, 
composed  of  water,  albumen  (.36  in  100)  and  todium 
chloride.  When  the  fat  is  absorbed  by  the  demands  of  the 
system,  its  place  is  filled  with  serous  fluid,  as  in  phthisis. 

^U^X'TION. — Its  function  is  to  surround  and  connect 
various  organs,  and  retain  them  at  certain  distances ;  at 
the  same  time  allowing  a  certain  amount  of  motion.  It 
also  forms  a  nidus  for  the  vessels  and  nerves,  fills  up  snaces 
between  different  organs,  and  when  the  meshes  are  filled 
with  fat,  gives  rotundity  to  the  body.  In  some  parts  of  the 
body  it  is  very  dense,  and  has  received  the  name  of  a  fibrous 
membrane,  as  in  the  phar3'^nx,  sheaths  of  vessels,  etc.  It 
forms  sheaths  for  the  muscles,  and  the  bundles  and  fasciculi 
of  which  they  are  formed.  It  also  forms  sheaths  for  the 
vessels  and  nerves.  It  attaches  the  membranous  expansions 
as  the  rcucous,  cutaneous,  serous  and  synovial  membranes, 
to  the  structures  M'^hich  they  surround  and  embrace,  and  re- 
ceives the  name  of  sub-mucous,sub-cutaneous,sub-serous  and 
sub-synovial  areolar  tissue,  respectively. 


Tl 
cells 
in  w 
fouii 
bon( 
of 
muc 
anc 
euro 


ADIPOSE  TISSUE. 


65 


ADIPOSE  TISSUE. 

This  was  formerly  described  as  areolar  tissue,  with  fat 
cells  imbedded  in  its  meshes.  It  exists  hovr-ever,  iu  parts 
in  which  not  the  slightest  trace  of  areolar  tissue  can  be 
found,  as,  for  exam[>lu,  in  the  cancellous  tissue  and  marrow  of 
bones.  On  the  other  hand,  the  areolar  tissue  in  many  parts 
of  the  body  is  entirely  destitute  of  fat,  as  e.  (j.,  beneath 
mucous  membranes,  in  the  cutis  vera,  between  the  tectum 
and  bladder,  in  the  cranial  cavity,  eyelids,  epicranial  apon- 
eurosis, scrotum,  penis,  etc,  but  in  other  parts  of  the  body 
they  are  associated  together.  Adipose  tissue  is  found  in 
abundance  in  the  subcutaneous  areolar  tissue,  called  panni- 
cuius  adiposua.     It  is  entirely  absent  in  embryonic  life. 

Physical  Appearance  and  Properties. — Itiscompo.ed 
of  cells  or  vesicles  containint;  fat,  which  vary  in  size  from 
joa  to -J J^ J  of  an  inch  (83  to  31  mmm)  (Fig.  2J ).  They 
are  usually  deposited  in  cluisoers,  being  held  together  by  a 
mesh  of  capillaries,  which  surrounds  them,  and  fi-om  which 
fig.  22.  they  derive  their  nutiinnent 

This  constitutes  a  lobule. 
When  the  adipose  tissue  ex- 
ists in  considerable  quan- 
tity, the  lobules  are  held  to- 
gether by  areolar  tissue,  con- 
stituting a  mass  of  fatty  tis- 
sue. It  is  abundantly  sup- 
plied with  blood-vessels,  but 
Fat  cells  of  adipose  tissue.  Donerves  or  lymphatics  have 

been  traced  into  its  substanee.  At  an  early  period  of  its 
formation,  the  cell  or  vesicle  possesses  a  nucleus  and  nu- 
cleolus, the  nucleus  being  imbedded  in  the  cell-wall ;  but 
they  disappear  at  maturity,  being  obscured  by  the  oily  con- 
tents of  the  cells.  The  cells  or  vesicles  are  round,  when 
isolated^  but  become  polyhedral  from  the  flattening  of  their 
walls  against  each  other. 


They  are  believed  by  some  to  ori- 


c 
I. 

h 

»; 

■II 


mr, 
1*1  ^ 


fiG 


TISSUES. 


ginate  from  connective  tissue  corpuscles  by  their  transforma- 
tion into  fat  cells.  They  are  long-lived,  and  cxosmosis  of  the 
fat  is  prevented  by  the  constant  moistening  of  their  walls, 
by  a  thin  serous  fluid  which  surrounds  them,  on  the  same 
principle  that  a  moist  bladder  will  retain  fatty  matter, 
while  a  dry  one  allows  it  to  exude.  The  cell  wall  in  fat 
cells  can  bo  distinctly  seen  in  a  collapsed  condition,  after 
dissolving  out  the  fat  by  means  of  etlier  ;  the  nucleus  Is 
then  also  readily  seen  by  tinging  with  carmine. 

Origin  and  Function. — This  tissue  is  formed  partly 
from  the  fat  used  as  food,  and  also  by  a  chemical  transfor- 
mation from  the  starch  and  sugar  ])resent  in  the  ditterent 
articles  of  diet.  This  process  is  accelerated  by  an  imperfect 
su|)ply  of  oxygen,  as  is  seen  in  the  fattening  of  animals 
which  are  closely  penned  up.  It  is  also  formed  in  the 
interior  of  most  cells  of  the  body,  when  undergoing  retro- 
grade changes,  as  in  fatty  degeneration.  It  fills  up  spaces 
otherwise  unoccupied,  gives  rotundity  to  the  body,  forms  a 
delicate  pad  or  cushion  to  facilitate  the  action  of  movable 
])arts,  as  at  the  base  of  the  heart,  behind  the  eye-ball  etc., 
and  from  being  a  bad  conductor  of  heat,  it  prevents  its  too 
rapid  escape  from  the  animal  body.  This  is  exemj^lified  in 
those  animals  possessing  little  hair  on  their  skin,  in  which 
there  is  a  large  quantity  of  adii)ose  tissue  beneath  tl'a 
integument.  In  other  instances  it  gives  ease  to  the 
gliding  movements  of  parts,  and  protects  them  from  the  ill 
effects  of  sudden  changes  of  tem])erature,  as  the  adipose 
tissue  of  the  omentum.  As  fat,  it  supplies  combustible 
material  for  the  maintenance  of  the  animal  heat  of  the  bodv. 
It  is  stored  away  in  the  body,  to  be  used,  when  necessary, 
to  maintain  animal  heat,  and  as  a  sourcQ  of  nourishment, 
as  in  the  hyberuating  animals,  the  process  of  absorption 
of  fat  being  facilitated  by  the  alkaline  condition  of  the 
serous  fluid  by  which  the  cells  are  surrounded.  (See  oils 
and  fats). 


Tl 
parti- 


CARTILAGE. 


67 


CARTILAGE. 

This  is  a  very  simple  form  of  tissun,  and  is  found  in  many 
parts  of  the  body.  In  some  of  the  lower  animals,  as  fishes, 
the  skeleton  is  formed  entirely  of  this  tissue,  as  the  skate, 
sturgeon,  etc. 

Physical  Appearance  and  Properties. — Its  color  va- 
ries from  pearly  white  to  light  yellow,  and  it  is  possessed  of 
a  considerable  degree  of  elasticity,  flexibility  and  cohesive 
power.  It  yields  chondrinc,  when  boiled.  Cartilage  con- 
sists of  cells  imbedded  in  a  hyaline  or  inter-cellular  sub- 
stance, or  matrix.  The  cells  ,,|^,  o.., 
are  contained  in  cavities  or 
lacunjio  in  the  intercellular 
substance.  Some  of  these 
cavities  are  lined  by  a  thin 
membrane,  the  cartilage  cap- 
sule ;  in  other  instances  the 
cells  appear  to  blend  with 
the  intercellular  substance 
(Fig.  23).  The  cells  are  round 
or  oblong,  and  vary  in  size  from  ^fj^  to  ^rA,g  of  an  inch,  (55.5 
to  12.5  mmm).  Each  cell  contains  a  nucleus  and  one  or  more 
nucleoli.  The  nucleus  varies  in  size  from  ^^'..o  to  j^^^  of  an 
inch,  (10  to  6.2  mmm.)  and  sometimes  contains  fat  globules, 
as  a  result  of  some  peculiar  metamorphosis  of  the  contents. 
Cell  growth  takes  place  by  the  process  of  multiplication  by 
subdivision,  and  parent  cells  are  frequently  seen  containing 
two  or  more  young  cells. 

The  intercellular  substance  is  either  homogeneous,  granu- 
lar, or  fibrous. 

Cartilage  is  divided  into  two  great  classes  :  Temporary 
and  Permanent ;  the  former  constitutes  the  original  frame 
work  of  the  body,  except  portions  of  the  vault  of  the  cra- 
nium and  bones  of  the  face  ;  and  is  sup[)lanted  by  bone 
during  development    and   growth  ;  the  latter  is  found  in 


Hyaline  (teiniioniry)  oartilago  licuoming 
traiHfonned  into  l)c>ne  subMtanco.  Hy- 
aline sul)stauce  witli  cartilaj^e  cells  imbed- 
ded in  it. 


r 
c 

I 

•it 


If 
f.  ■ 


1 

.» 

I 

f 


G8 


TISSUES. 


Fig.  24. 


different  parts  of  the  body  and  is  not  transformed  into  bone. 

It  is  also  divided  into  three  classes  according  to  the 
character  of  the  intercellular  substance,  viz.  :  Hyaline, 
elastic  or  reticular,  and  connective  tissue  or  fibro-cartilage. 

Hyaline  Cartilage. — This  variety  of  cartilage  embraces 
temporary,  articular  and  costal  cartilage,  also  the  cartilages 
of  the  nose,  larynx,  trachea  and  bronchi,  except  the  epiglottis 
and  cornicula  laryngis.  In  all  these  situations  the  in- 
tercellular substance  is  homogeneous  or  finel}'  granular,  but 
occasionally  in  old  costal  cartilage  a  few  indistinct  fibres 
may  be  seen.  In  temporary  cartilage  the  intercellular  sub- 
stance is  not  very  abundant ;  but  the  cells  are  numerous, 
and  placed  at  nearly  equal  distances  apart.  They  are 
rounded  or  oval,  and  vary  in  size  from  y^oTT  to  tbVo  <>f  an 
inch,  (16  to  12.5  mmm.)  the  nuclei  being  finely  granular. 

Near  the  seat  of  ossification  the 
cells  are  arranged  in  rows,  run 
ning  towards  the  ossifying  part, 
and  become  hardened  by  intersti- 
tial or  secondary  dej)osit  of  cal- 
careous salts  (Fig.  24).  In  the 
cartilage  of  the  ear  in  rats,  mice, 
and  other  small  animals,  and  also 
in  the  human  chorda  dorsalis  in 
early  foetal  life,  the  intercellular 
substance  is  very  small  in  quan- 
tity and  the  cells  are  closely 
packed  together.  This  constitutes 

Cartilage  cell8  in  rows  at  the  seat  of    the  SO-Callcd  Ccllular  Cartilage, 
ossification. 

In  articular  cartilage  which  is  found  in  joints,  covering 
the  articular  surface^  of  bones,  the  intercellular  substance  is 
more  abundant  than  in  temporary  cartilage,  and  presento  a 
finely  granular  appearance.  The  cells  are  rounded  or  oval, 
varying  in  size  from  y^^^  to  ^^^  of  an  inch  (19  to  27.8 
mmm).     Near  the   surface   of  the  cartilage,  the  cells  are 


ages, 


CARTILAGE. 


69 


numerous,  and  arranged  in  flattened  groups,  lying  with  their 
planes  parallel  to  the  surface.  This  appearance  has  been 
mistaken  by  some  physiologists  for  a  layer  of  epithelium. 
In  the  interior  of  the  cartilage,  the  cells  assume  a  linear 
direction  pointing  towards  the  surface.  This  serves  to  ex- 
explain  the  disposition  this  form  of  cartilage  has,  to  split  up 
in  a  direction  perpendicular  to  the  surface.  In  costal  car- 
tilage, the  intercellular  substance  is  very  abundant,  finely 
mottled  and  sometimes  indistinctly  fibrous.  The  cells  are 
larger  than  in  any  other  cartilage  of  the  body,  being  from 
-s\^  to  -i\^  of  an  inch  (38  to  55.5  mmm)  in  diameter.  Some 
contain  two  or  more  nuclei,  which  are  transparent,  and 
others  contain  nuclei  and  fat  globules.  The  cells  often 
assume  a  linear  arrangement,  the  rows  being  turned  in 
different  directions — probably  the  result  of  the  growth  of 
the  cells  by  subdivision  from  the  parent  cell,  and  their  sub- 
sequent separation  from  each  other  in  a  linear  manner. 
Calcification  of  cartilajje  sometimes  occurs.  It  consists  in  a 
deposition  of  lime  salts  around  the  cells  or  cell  groups,  until 
the  whole  intercellular  substance  presents  a  dark  granular 
appearance  (Fig.  29.)  This  calcified  cartilage,  however,  d  jes 
not  become  bone. 

Elastic  or  R:.ticular  Cartilage. — This  is  of  a  yellow- 
ish color,  arranged  in  the  form  of  plates  or  lamellae  of  various 
thickness,  and  enters  into  the  formation  of  the  external  ear, 
epiglottis,  cornicula  laryngis.  Eusta- 
chian tubes  etc.  These  plates  serve  to 
maintain  the  shape  of  tubes  or  pass- 
ages, which  require  to  be  kept  open, 
without  the  expenditure  of  vital 
force.  It  approaches  in  character  to 
the  fibro-cartilage.  The  intercellular 
substance  is  permeated  by  a  clear  net- 
work of  fine  elastic  fibres.  The  cells 
are  numerous  and  vary  in  size  from 
T.V^  to  ^1^  of  an  inch  (19  to  27.8  ^f^^^^^^^^^T^^ 
mmn .)  in  diameter  (Fig.  25).  Frey!'""'  "'"^  "'  *'''  '*"^'- 


Fig.  25. 


c 
c 


I 


HtT, 


(0 


TISSUES. 


CoNNKCTiVE  Tissue — or  Fiimo-CAUTILAOE. — Film)  car- 
tilage consists  of  a  mixture  of  connective  tissue  and  cartilage 
cells  in  various  proportions.  It  exists  in  four  forms,  luter- 
articular,  Connecting,  Circumferential  and  Strnti for.it. 

The  interarticular  Jihro-cartilages  ai'e  flattened  lamel- 
Ire  of  diflorent  shapes,  placed  between  the  cartilages  of 
the  temporo-maxillary,  sterno-clavicular,  acromio-clavicular, 
wrist  and  knoe-joints.  They  are  free  on  both  surfaces ; 
thinner  at  the  centre  than  at  the  circumference,  and 
are  held  in  position  b}'^  the  surrounding  ligaments.  1'heir 
use  is  to  increase  the  depth  of  the  articular  surfaces  ; 
to  moderate  the  effects  of  great  pressure  ;  as  a  cushion,  to 
deaden  the  intensity  of  shoclcs;  to  give  ease  to  the  gliding 
movements  of  these  joints  ;  and  to  iucrease  the  extent  of  the 
svnovial  membrane  for  secretion. 

The  connecting  Jibro-cartdages  are  placed  between  the 
bony  surfaces  of  those  joints  which  possess  very  little  mo- 
bility ;  as  between  the  bodies  of  the  vertebrjv,  and  the  sym- 
])hysis  of  the  pubcs,  and  serve  to  connect  them  together. 
They  are  in  the  form  of  discs,  com[)o&ed  of  concentric  rings 
of  fibrous  tissue  and  cartilaginous  laminjv  placed  alter- 
nately ;  the  former  j)redominating  towards  the  circumfer- 
ence ;  the  latter,  towards  the  centre. 

The  circmnfcrential  variety  comisis  of  a  rim  of  fibro-car- 
tilage  which  surrounds  the  margin  of  some  of  the  articular 
surfaces,  and  serves  to  deepen  the  cavity  ;  as,  e.g.,  the  glenoid 
and  cotyloid  cavities. 

The  stratiform  Jibro-cartilage  lines  the  grooves  through 
which  the  tendons  of  certain  muscles  pass  ;  as  e.g.,  the  bici- 
pital groove. 

Vascular  SurrLY.— Cartilage  is  chiefly  supplied  by  im- 
bition.  It  is  covered  by  a  layer  of  white  tibrous  tissue, 
contnining  vessels,  called  the  perichondrium,  which  corres- 
ponds to  the  periosteum  of  bones.  From  this  covering  the 
cartilage  leceives  its  nutriment.  When  the  cartilage  is  thin 
no  vessels  penetrate  it ;  but  when  it  is  more  than  ^  of  an 


GELATINOUS  AND  RETICULAR  TISSUES. 


71 


inch  in  thickness  as  in  costal  cartilage  it  contains  canals  for 
their  transmission. 

Articular  cartihige  is  not  covered  by  perichondrium.  It 
derives  its  nutrition  by  imbibition  from  the  vessels  of  the 
synovial  membrane  which  skirt  the  circumference  of  the 
cartilage,  and  also  from  those  of  the  cancelli  of  the  adjacent 
bone,  which  are  separated  from  the  cartilage  by  the  articu- 
lar lamella.  The  vessels  of  the  synovial  membrane  pass 
forward  to  the  margin  of  the  cartilage,  and  then  return  in 
loops,  and  those  of  the  cancellous  tissue  pass  to  the  internal 
surface  of  the  articular  lamella,  form  arches,  and  return  to 
the  substance  of  the  bono. 

Fibro-cartilage  is  supplied  by  the  vessels  of  the  synovial 
membrane  and  j)erichondrium,  with  which  it  is  invested. 

GELATINOUS  AND   RETICULAR  CONNECTIVE  TISSUES.   ^ 

Gelatinous  tissue  constitutes  the  semi-solid  substance 
which  forms  the  vitreous  humor  of  the  eye,and  the  jelly-like 
substance  which  covers  the  umbilical  cord  (Whartonian 
jolly).  It  consists  of  a  soft  homogeneous  intercellular  sub- 
stance in  which  are  imbedded  a  number  of  rounded  trans- 
parent cells.  A  higher  development  of  the  gelatinous  tissue 
is  found  in  the  so-called  enamel  organ  of  the  growing 
tooth.     The  cells  in  this  case  are  stellate  in  form. 

Reticular  connective  tissue  is  found  in  the  lymph  glands, 
and  lymphoid  organs,  as  the  tonsils,  thymus  gland,  Peyers 
glands,  Malpighian  corpuscles  of  the  spleen,  etc.  It  con- 
sists of  a  delicate  areolar  tissue  in  the  meshes  of  which  lie 
innumerable  lymphoid  cells  (white  corpuscles).  It  is  some- 
times called  adenoid  tissue,  and  is  believed  to  be  a  modified 
form  of  connective  tissue.  It  is  built  up  of  stellate  nucleated 
cells,  the  arms  of  which  are  united  like  threads,  and  form 
meshes  in  which  the  lymphoid  cells  are  situated.  The 
meshes  are  usually  rounded,  but  may  assume  an  elongated 
form. 


I. 

I' 

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»-< 

E 

C 

r*' 
I 

«•' 
>ni 


72 


TISSUES. 


BONE. 

This  constitutes  the  solid  frame-work  of  the  body.  It 
forms  organs  of  support,  levers  for  motion,  or  it  encloses 
cavities,  and  protects  delicate  organs,  as  the  br^in,  heart, 
lungs,  &c. 

Physical  Appearance  and  Properties. — It  is  a  hard, 
dense,  opaque  substance,  of  a  whitish  color,  and  possesses  a 
considerable  degree  of  elasticity.  It  consists  of  an  organic 
or  animal,  and  an  inorganic  or  earthy  material,  intimately 
blended  together;  the  animal  matter  giving  to  the  bone  its 
elasticity  and  toughness ;  the  earthy  part  its  hardness  and 
density.  The  animal  matter  may  be  separated  from  the 
earthy,  by  steeping  the  bone  in  dilute  nitric  or  muriatic  acid. 
In  this  way  the  earthy  matter  is  dissolved  out,  and  the 
bone  becomes  quite  pliable — so  much  so,  that  the  fibula,  if 
so  treated,  can  be  drawn  into  a  knot.  The  earthy  constitu- 
ents may  be  obtained  by  burning  the  bone  in  an  open  fire. 
By  this  means  the  animal  matter  is  entirely  consumed,  and 
the  earthy  part  remains  as  a  white  brittle  substance.  The 
relative  proportion  of  these  two  substances  varies  in  differ- 
ent persons,  and  in  the  same  person  at  different  periods  of 
life.  In  the  child,  the  animal  matter  forms  about  half  the 
weight  of  the  bone  ;  in  the  adult  about  33^  per  cent.,  and 
in  old  Age  about  25  per  cent.  In  certain  diseases  of  the 
bones,  as  rachitis  or  "  rickets  "  and  mollities  ossium,  there 
is  a  deficiency  of  earthy  matter,  and  in  fragilitas  ossium,  a 
deficiency  of  animal  matter.  Bone,  when  boiled,  yields  gela- 
tine, and  from  the  earthy  matter  may  be  obtained  granules, 
from  TTjVff  to  TToou  of  an  inch,  (4.  to  1.7  mmm)  in  diameter. 

Chemical  Constituents. — In  100  parts : — 

Organic  matter — Areolar  tissue,  Blcxjd-vessels,  Nerves  and  Fat  33- 30 

rLime  Phosphate 5I-04 

T            .                Lime  Carbonate 1 1. 30 

Inorganic  or       )  Calcium  Fluoride 2.60 

Earthy  matter.     1  Magnesium  Phosphate 1. 16 

I  Soda  and  Sodium  Chloride 1.20 

100.00 


BONE. 


73 


Structure  of  Bone. — Bone  presents  two  varieties  of 
osseous  tissue.     The  one  is  dense,  firm  and  compact,  and 
always  situated  on  the  exterior  of  the  bone,  called  the  conx- 
pact  tissue ;  the  other,  loose  and  spongy,  enclosing  cells  or- 
cancelli,  and  situated   internally,  is  called    the  cancellous 
tissue.     In  the  extremities  of  the  long  bones,  the  cancellous 
tissue  is  most  abundant,  while  in  the  shaft  the  compact  tis- 
sue predominates.     In  short  and  flat  boues,  the  two  varie- 
ties are  more  evenly  distributed.    The  externjvl  surface  of.  I 
the  compact  tissue  (except  the  articular  lamella^  is  covered  ^ 
by  a  dense  fibrous  membrane,  the  periosteum.    The  interior 
of  the  long  bones  in  adult  life,  presents  a  cavity  called  the 
medullary  canal.     This  is  filled  with  the  so  called  marrow, 
which  is  of  a  reddish  or  yellow  color,  and  consists  of  vessels, 
nerves,  delicate  areolar  tissue,  fat  cells,  and  a  number  of 
lymphoid  cells.     The  latter  are    believed,  by   some,  to  be 
transformed  into  red  blood  corpuscles.     There  are  also  near 
the  surface  of  the  bone  marrow,  a  number  of  myeloplaxes  or 
giant  cells  (Fig.  14«  e.)     The  cancellous  tissue  also  contains 
marrow.     The    periosteum    is   abundantly   supplied   with 
blood  vessels,  and  is  intimately  attached  to  the  bone  ;  and 
if  separated  to  any  great  extent,  the  bone  perishes.     It  also 
sends    prolongations,   accompanied   with   vessels,  through 
numerous   foramina  in   the   bone   into  the  canals   of  the 
compact   tissue   for   its   supply.     It   is   now   settled  that 
the  medullary  cavity  is  not   lined  by  a  membrane  corres- 
p(mding  to  the  periosteum  (endosteum),  the  marrow  being 
applied  directly  to  the  bone. 

If  a  transverse  section  from  the  shaft  of  a  long  bone  be 
examined  under  the  microscope,  a  number  of  apertures,  sur- 
rounded by  a  series  of  concentric  rings,  may  be  seen.  These 
apertures  are  sections  of  the  medullary  or  Haversian  canals 
(named  after  the  discoverer,  Cloptou  Havers),  and  the  rings 
are  sections  of  the  lamellae  which  surround  the  canals.  Sur- 
rounding the  Haversian  or  medullai-^  canals,  in  a  concentric 
manner,  may  be  seen  a  series  of  dark  spots  or  centres,  called 
lacunae.     These  communicate  with  each  other,  and  with  the 


c 

c 

M* 

c 

1. 

fr 

ft*. 

»-.-• 

«< 

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1. 

*.v 

!••' 

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»ti, 

€!(•»■ 

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i-ti 

Hi'' 

tn. 

M>  t.  ■> 

74 


TISSUES. 


Haversian  canalM,  by  minute  tubes,  called  cnnalieiili  or 
pores.  The  whole  constitutes  a  Haversian  system,  and  is 
a  provision  made  for  the  supply  of  the  comi)act  tissue. 

FItr.  26. 


Transverse  seotion  of  tlie  slmft  o(  the  lunnenis  x  150,  Three  Havorsiiin  canals  arc  soon 
with  eoiu'entric  rings  ;  also  tlio  corjiugcles  or  laeunai  with  the  canalieuli  extending  in  all 
directions. 

The  Haversian  canals  in  the  long  bones  run  nearly 
parallel  to  each  other  and  to  the  long  axis  of  the  bone ;  but 
in  the  irregular  and  flat  bones,  they  are  irregular  in  their 
direction.  They  vary  in  size  trom  j,',o  to  io'do  of  an  inch 
(125  to  12.5  mmni)  and  communicate  freely  with  each  other 
and  with  the  outer  and  inner  surfaces  of  the  conijiact  tissue, 
by  means  of  transverse  and  oblique  canals,  (Fig.  27).     They 

give  passage  to  small  arteries  and 
nerves  for  the  supply  of  the  bone. 
The  small  arteries  are  derived  from 
the  nutrient  artery,  the  vessels  of 
the  periosteum  and  marrow.  The 
laminae  which  surround  the  Haver- 
sian canals  vary  in  number  from  8  to 
15,  and  are  called  the  Haversian 
lamellae.  Besides  these,  some  ap- 
Longitudinai  section  of  bone,  pear  to  be  arranged  concentrically, 

Bhowing  the  Haversian  canals  and  ,     ,  in  i 

their  branches.  around  the  mcduliary  canal  or  mar- 

row of  the  shaft;  these  are  called  circumferential,  and  others 


BONE. 


75 


are  situated  between  the   Haversiau  systems,  called  inter- 
stitial lanielhn. 

LA.(JUNi*l — The  lacuna^  or  bone  cells  are  arranged  in  con- 
centric circles  around  the  Haversian  canals.  They  are  small 
cavities  of  a  setni-lunar  shape,  the  concavity  being  turned 
towards  the  Haversian  canals,  and  vary  in  size  from 
nsVo  to  j„Vif  of  an  inch,  (1G.5  to  12.5  mmm).  They  are 
reservoirs  for  the  plasma  of  the  blood,  previous  to  its  ab- 
Fitf.  28.  sorption  Ijy  the  tissue,  and  each  contains  a 
nucleated  membraneless  ccll.or  bone  corpuscle, 
which  is  homologous  with  the  connective  tis- 
sue corpuscle,  and  which  in  all  probability 
sends  prolongations  into  the  canaliculi. 

Canaijculi. — These  aresniall  tubes  orpores, 
which  issue  from  all  parts  of  the  circtimfer- 
encc  of  the  lacuna'.  They  communicate  with 
A  lai-mm  from  tliosc  fVoiu  adjaccut  lacuua^  and  some  open  on 
c.f  tiio  inouso;  a,  tlic  ircc  surtacc  01  the  bone.  iJy  this  ar- 
tiiu  lu.iie  cull.  rangement,  the  plasma  ot  the  blood  is  carried 
into  every  part.  They  vary  in  size  from  vs^ttit  to  ^oAuw  of 
an  inch  (I.G5  to  1.25  mmm.)  in  diameter. 

In  cancellous  tissue,  and  in  the  ai'ticular  lamella  which 
supports  the  articular  cartilage,  there  are  no  Haversian 
canals,  and  the  lacuna?  are  larger  than  ordinary. 
Devklopmknt. — Bone  is   not  '■ij,'.29. 

directly  formed  from  temporary 
cartilage,  as  was  formerly  sup- 
posed. 

Ossification  commences  in  the 
cartilage  at  certain  points,  called 
jioints  or  centres  of  ossification, 
but  the  calcified  cartilage  (Fig 
29)  does  not  become  bone.  It 
dissolves  away,  and  in  the  sys- 
tem of  cavities  thus  formed  the 
bone  substance  is  developed  from    section  of  diaphysis  of  caitiiuffc ; 

,  .  ^  calciliud  cartilasfu ;  p,  iturichoiidriutn 

the  periosteum. 


r 

c. 

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n: 

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■1 

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76 


7  ISSUES. 


In  long  bones  there  is  usually  a  centi-al  ]>oint  for  the 
shaft,  and  one  for  each  extremity.  The  c(;ntral  jxjint  is 
called  the  diaphysis,  the  extremity  the  epiphys'us.  The 
point  of  ossification  of  a  process,  as,  e.  g.,  the  olecranon,  is 
also  called  the  epiphysis,  and  when  finally  joined  to  the 
shaft,  an  apojihijsis.  The  period  at  which  ossification  begins, 
varies  in  different  bones.  The  earliest  is  the  clavicle,  which 
begins  about  the  fouith  week  of  foital  life  ;  next,  the  lower 
jaw,  then  the  ribs,  vertebiJi;,  femur,  humerus,  tibia,  uj^per 
jaw,  etc.,  in  order  of  succession. 

n-.  :m. 


Section  of  epipliysis  showing  the  process  of  ossification.  1. — Cartilage  colls  imbedded  ii* 
hyaline  substance.  2. — Cavernous  tissue,  the  calcified  cartilage  having  become  liquefied. 
3.— Ossifying  portion,  (a)— Cavernous  or  medullary  spaces  shown  empty,  (b)— The  same 
filled  with  cells,  (c)-  Remains- of  the  calcified  cartilage,  (d)— Medullary  spaces  in  which 
lamelltB  of  bone  tissue  l^ave  been  foniied  from  the  osteoblasts,  (e)— Developing  bone  cell.. 
(f,  g,  h) — Imbedded  bone  cells  or  lacuuic. 

In  the  transformation  of  temporary  cartilage  into  bone 
preparatory  changes  take  place  which  consist  in  its  becom- 


BONE. 


it 


ing  .soft  and  vascular,  the  vessels  growing  in  from  tlio  ]iori- 
chondrium.     The  cartilage  cells  multiply  and  form  cylindri- 
cal piles  or  columns,  (become  ranked),  sejjaratod  from  each 
other  by  trabecuhu  of  intercellular  substance  which  is  be- 
coming calcified  ('Fig's.  24  and  30).   The  calcified  substance 
soon  after  liquefies  in  places  so  as  to  form  cavernous  spaces 
or  areoUu,  which  contain  groups  of  cartilage  cells,  and  basis 
substance.    The  cells  next  the  ])eriphery  of  these  cavernous 
or  medullary  sj)aces  and  which  resemble  a  layer  of  epithe- 
lium, beconie  altered  in  shape  and  are  called  osteoblasts. 
These  coalesce  with  each  other  and  with  the  inteicellular 
substance  to  form  theyir.s^  lamella  of  bone  tissue;  while  here 
and  there  one  of  the  osteoblasts  is  pushed  out  of  line  or  in- 
dented,  and    forms   a   lacuna   or   bojio    cori)uscle.       This 
process   is   again   and   again   repeated   by  the  production 
of  cells  from  the  basis  substance  until  the  formation  is  com- 
pleted.    Each  lacuna  throws  out  arms  or  projections  in  diff- 
erent directions,  which  meet  others  from  adjacent  lacunae 
and  in  this  way  canaliculi  or  pores  are  formed.     This  endo- 
chondral bone  which  is  so  irregular  and  cavernous,  is  very 
different  however  from  the  beautiful  regularity  of  perma- 
nent bone  tissue.    It  undergoes  a  change.    According  to  some 
the  endochondral  bone  becomes  liquified  and  absorbed  in 
order  to  permit  of  the  formation  of  medullary  canals,  and  a 
new  formation  of  bone  takes  place  from  the  periosteum, 
into  which  the  perichondrium  has  been  changed.     Others 
deny  the  liquefaction  theory,  and  maintain  that  the  change 
is  due  to  interstitial  growth  alone  ;  we  rather  incline  to  the 
absorption  theory.     It  is  now  a  w^ell  known  fact,  that  living 
periosteum  has  the  power  of  generating  bone  tissue,  from  the 
osteoblasts  of  its  deepest  layer.   According  to  the  absorption 
theory,  while  the  liquefying  process  is   going   on   in   the 
endochondral    bone,   the    osteoblasts    of    the    periosteum 
grow  downwards  in  cones  (osteoblast  cones.)     These  osteo- 
blast-cones  produce  the  Haversian  lamelUie,  while  the  flat  os 
teoblast  layer  immediately  beneath  the  periosteum  forms 
the  general  or  circumferential  lamelh^.      This  also  explains 


r 
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i 


78 


r/ss[/Es. 


the  increase  in  thickness  of  the  bone  during  growth  and 
development.  During  ordinary  repair,  absorption  from 
within  and  deposition  from  without  are  continually  going 

on. 

The  ossification  in  the  vault  of  the  cranium  and  bones  of 
the  face,  in  which  there  is  no  tem])orary  cartilage,  is  called 
intra-memhranous  orectosteal.in  contradistinction  to  intra- 
<carHlmfmons  orendosteal.  These  bonesare  formed  from  asoft, 
f(i'tal  connective  tissue  in  which  are  found  nuclei  and  osteo- 
blasts, the  ])r()cess  of  origin  of  bono  being  the  same  as 
when  formed  from  periosteum.  Some  modern  investigators 
also  favor  the  view  that  bone  may  be  formed  by  the  direct 
transformation  of  cartilage  into  bone  tissue,  or  by  the  de- 
position of  calcareous  matter  in  connective  tissue.  The  latter 
may  be  the  explanation  of  the  formation  of  the  so-called 
callus  in  the  repair  of  bone. 

Growth. — The  growth  of  bone  takes  place  by  layers 
formed  in  succession  on  its  external  surface — exogenous — 
and  also  in  an  interstitial  manner.  Bones  increase  in  length 
by  additions  between  the  points  of  ossification,  and  by 
accessions  of  osseous  tissue  to  the  extremeties.  This  may 
be  shown  by  inserting  metallic  pegs  in  the  shaft  at  certain 
■distances  apart,  when  it  will  be  .seen  that,  notwithstanding 
the  increase  in  length  of  the  bone,  the  distance  between 
them  remains  the  same. 

Bones  increase  in  diameter,  by  additions  of  osseous  tissue 
on  their  exterior.  The  osseous  ti.ssue  thus  added  is  not  a 
mere  lamina  of  bone,  but  consists  of  complete  Haversian 
systems,  the  earlier  systems  being  covered  over  by  the  more 
recent  ones.  This  may  be  demonstrated  by  feeding  animals 
with  madder.  The  coloring  principle  is  precipitated  with 
the  lime  phosphate,  and  on  examination,  beautiful  crimson 
rings  are  seen  encircling  the  Haversian  canals.  This  ap- 
pearance is  confined  chiefly,  to  the  external  or  vascular  sur- 
face. When  the  madder  has  been  given  at  intervals,  colored 
and  colorless  portions  alternate  with  each  other.  The  color 
remains  a  long  time,  indicating  a  slow  change  of  this  tissue. 


TEETH. 


7D 


In  early  life  there  is  no  medullary  canal  in  the  shaft  of 
the  long  bones,  its  place  being  filled  with  cancellous  tissue. 
This  tissue,  however,  becomes  gradually  absorbed  as  age  ad- 
vances, until  about  the  twenty-fourth  year,  when  the  canal 
is  completely  formed  and  tilled  with  marrow. 

Tekth. — There  are  two  sets  of  teeth  with  which  the  hu- 
man subject  is  ])rovided.  The  first  set  aj)pear  in  childhood 
and  are  called  tem'porary  or  deciduous  teeth.  They  are 
twenty  in  number, — four  incisors,  two  canine,  and  four 
molars  in  each  jaw.  The  .second  set  are  called  permanent^ 
and  are  thirty-two  in  number, — four  incisors  or  front  teeth 
two  cuspids  (one  on  each  side  of  the  incisors),  four  bicuspids 
two  on  each  side),  and  six  molars  (three  on  each  side),  in 
each  jaw.  Each  tooth  consists  of  the  crown  or  exposed 
part,  the  neck,  the  constricted  part  beneath  the  gum,  and  a 
single  or  multiple  fcmg  or  root  imbedded  in  the  jaw,  and 
contains  within  it  a  pulp  cavity.  The  bicuspids,  and  the 
molar  teeth  of  the  lower  jaw,  have  each  two  fangs ;  the 
molars  of  the  upper  jaw,  three. 

The  pulp  consists  of  vessels,  highly  sensitive  nerve  fila- 
ments and  areolar  tissue,  which  enter  by  an  opening  at  the 
extremity  of  the  fang.  It  also  contains  dentinal  cells  or 
odontoblasts,  from  which  the  dentine  is  formed.  These 
odontoblasts  are  oval  in  shape,  ^^^,Q  to  n.Vo  of  an  inch  (2  to- 
3  mmm)  in  diameter,  and  send  some  of  their  fine  thread-like 
processes  into  the  dentinal  tubuli.  The  pulp  cavity  may  bo 
compared  to  the  Haversian  canals  of  bone.  The  solid 
structure  of  the  tooth  is  composed  chiefly  of  dentine,  covered 
with  a  thin  layer  of  enamel  on  the  crown,  and  bone  tissue 
(crusta  petrosa)  on  the  fang. 

Dentine  consists  of  minute,  wavy  tubes,  dentinal  tubulin 
which  lie  parallel  to  each  other  and  open  into  the  pulp 
cavity,  being  arranged  vertically  on  the  summit,  and 
horizontally  on  the  sides.  The  tubuli  are  about  sjh-^v  to- 
TTooij  of  an  inch  (1  to  2  mmm.)  in  diameter,  and  are  imbed- 
ded in  a  dense,  homogeneous  substance — the  intertubular 
tissue  or  matrix.    They  divide  and  subdivide  dichotomously 


c 
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«0 


TISSUES. 


Kin,  ■■»!. 


AS  they  pass  towards  the  surface,  sometimes  terminating  in 

inter-globular  spaces  resembling 
lacuntv, and  convey  nourishment 
for  the  su[)ply  of  the  enamel. 
The  chemical  composition  of 
dentine  is  similar  to  bone,  with 
a  predominance  of  the  earthy 
matter,  in  the  proportion  of 
seventy-two  earthy,  to  twenty- 
eight  per  cent,   animal   matter. 

Sometimes  the  matrix  pre- 
sents lamella'  arranged  concen- 
trically with  the  pulp  cavity. 

Enamel  is  the  hardest  tissue 
of  the  body,  and  forms  a  cov- 
erinjj:  to  the  dentine  of  the 
crown  of  the  tooth.  It  con- 
sists of  a  congeries  of  minute, 
solid,   hexagonal    rods,    which 

Section  of  tooth  fiinn'.      a,  frusta  lie-  ii    '  x  i.i  j. 

trosa,  or  ooiii'.tit  io\eniitj;  I),  granular  uro  ])arallei  to  oue  anotliei',  rest- 

or  Tonii's' lavorwitii  intL'rulo'.iularsiiacos;   .  ,  i  -i  xi. 

c,  dutitinc ;  d,  .ioiitinai  tii'.uiii.  mg  oy  ouo  cxtreuuty,  on    tno 

dentine,  tlio  other  being  covered  by  a  tough  membrane 
Tsiuo-  tc  5  0  00  0-  (1.0  to  .8  nnnm.)  of  an  inch  in  thickness, 
called  the  CHtlcle  of  the  enamel.  They  are  arranged  verti- 
cally on  the  summit,  and  horizontally  on  the  sides,  like  the 
dentinal  tubuli,  and  are  about  ks^s-^  to  ToVtir  of  an  inch 
(4.5  to  3.G  mmm.)  in  diameter.  Small  spaces  are  left  be- 
tween the  rods  at  the  denlinal  surface  to  allow  of  the 
jienneation  of  fluids  from  the  dentinal  tubuli,  for  the 
supply  of  the  enamel.  It  consists  of  90.5  parts  earthy,  and 
3.5  parts  animal  matter. 

The  bone  covering  the  fangs  is  called  crusta  'petroaa,  or 
cement  covering.  In  structure  and  chemical  composition 
it  resembles  true  bone,  but  without  any  lamellar  arrange- 
ment '^r  Haversian  canals. 

Development  of  the  Teeth. — The  teeth  are  essen- 
tially dermal  structures  which  have  become  calcified,  the 


^-'r*vi^^- 


TEErtf. 


81 


epitheruua  f'onn"m<^    the  enamel,  and  tlie  subjacent  tissue, 

the  dentine  and  cement.     About  the  sixth  week  of  IVi'ital 

life,  a  rounded  thickening  or  projection  of  the  superficial 

Ki^.  32.  laycis  of  the  epithelium  of   the  jaw, 

appears  all  around  the  free  border.    At 

the  same  time  the  dee})  layerdipsdown 

into  the  subjacent  tissue  in  the  form 

^^  of  a  wetl;j;e,  and  forms  the  'primary' 

I  IWiili  \  I    III  11^^        enari'.el  geiin    (Fig.    32).       Here    and 

there  in  the  mucous  ti.ssue  of  the  jaw, 
corresponding  to  the  numl)er  of  teeth, 
a  convex  papillary  structure,  the  tooth 
a.  !''i'^,^'''jJjf"j.'/|.'Y,;^.^.^'"''jT  germ,  grows  upwards  towards  the  en- 
oSiriiS'liSri  amel  germ,  and  pushes  in  or  indents 
ya'ruiul^.' ''"  "'  ''"'  ^'"""'"'*''  i*^^  under  surface,  so  as  to  give  it  the 
form  of  a  cap  or  bell.  This  is  the  enamel  organ.  The  germs 
of  the  teeth  continue  to  grow  and  are  soon  enclosed  in  sac- 
culi,  (Fig.  33). 

Development  of  Enamel. — The  enamel  is  developed 
from  petrified  or 
calcified  epitheli- 
um. The  enamel 
oi'gan  bccomesse[»- 
arated  from  the 
point  of  origin  in 
the  epithelium  of 
the  jaw.  It  is 
lined  throughout 
with  cylindrical 
and  hexagonal  ei)i- 
thelial  cells,  cov- 
ering the  surface 
of  the  tooth  germ, 
and  reflected  at  its    ^^  p^„^^, 

ase  upon  the  innci  (,,.",,iiiarv) 
surface  of  the  sac    S^^'"'' 
cuius.     The  space  between  these  two  layers  is  filled  with  a 


I'i','.  s;!. 


1. 

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>vc  ;  )i,  remains  of  the  uiiaiiiel  \n:r\\\ ;  c,  unuinul 

■■pitlieliiini  on  its  outer  (wicriilar)  iiiid  inner 

;  il,  uiianiul  jfcrni  of  tliupeniiununt  tootli;  u, 

1,  section  of  inferior  luaxillu;  y,  Meclxei'H  car- 


89,  TISSUES. 

gelatinous  tissue,  whicli  is  the  pabulum  of  the  columnar  en- 
amel cells,  and  contains  a  few  stellate  cells.  These  columnar 
cells  upon  the  surface  of  the  tooth  germ  become  calcified,  and 
forn)  the  enamel  rods  which  are  completed  by  the  super- 
position of  cells,  and  their  subsequent  calcification. 

Development  of  the  Dentine. — The  dentine  is  devel- 
oped from  the  odontoblasts  of  the  tooth  germ,  by  a  process 
of  calcification.  It  commences  as  a  dark  area,  at  the  base 
of  the  enamel  germ.  As  development  proceeds,  the  cells 
or  odontoblasts  become  elongated  and  arranged  in  a  linear 
manner  vertically  to  the  surface  of  the  tooth  ge*-m;  the 
outer  portions  of  the  cells  become  calcified  and  form  the 
intertubular  tissue  or  matrix,  while  the  central  part  remains 
unchanged,  and  forms  the  dentinal  canals.  This  process 
gradrally  extends  inwards  while  the  vessels,  nerves,  and 
areolar  tissue  recede  until  they  come  to  occupy  the  central 
part,  which  is  called  the  pulp  cavity.  About  the  fifth 
month,  and  prior  to  the  calcification  of  the  temporary  teeth, 
a  " secondary  "  enamel  germ  begins  to  foini  on  the  inner 
side  of  the  original  one  for  the  production  of  the  "  perman- 
ent "  teeth.  These  pass  through  the  same  phases  of  devel- 
opment as  those  already  described  as  the  temporary  set. 

Eruption. — When  the  tooth  is  suflficiently  hard  to  enable 
it  to  pass  througli  the  gum,  the  eruption  takes  place.  The 
gum  is  absorbed  by  the  pressure  of  the  tooth  against  it, 
which  is  itself  pressed  up  by  the  increasing  size  of  the  fang. 
The  septa  between  the  dental  sacs,  at  first  fibrous,  soon 
ossify,  and  constitute  the  septa  of  the  alveoli  in  which  the 
fangs  are  lodged. 

PeHods  of  eruption  of  the  temporary  teeth. — The  teeth 
of  the  lower  jaw  precede  those  of  the  uj)per. 

Central  Incisors 7th  month. 

Lateral     "        7th  to  lotli      " 

Anterior  Molars 12th  to  I4tli      " 

Canines 14th  to  20tli      " 

Posterior  Molars i8tli  to  36th      " 


Perio 


MUSCLE.  83 

Periods  of  eruption  of  the  permanent  teeth  : 

First  Molars 6i  years. 

Middle  Incisors 7  " 

Lateral       "       8  " 

First  Bicuspids 9  " 

Second      •'        lo  " 

Canines ii  to  I2  " 

Second  Molars 12  to  14  " 

Wisdom  Teeth  (Dentes  Sapiential i/to  21  " 

The  teeth  of  the  lower  jaw,  also  precede  those  of  the 
upper  in  the  permanent  set. 

MUSCLE. 

Many  cells  of  the  body,  and  certain  tissues  possess  the 
power  of  changing  their  form,  from  time  to  time,  as  the 
white  corpuscles,  cartilage  cells,  cilia,  spermatozoa,  connec- 
tive tissue,  etc.,  but  the  muscles  are  alone  those  organs  by 
which  the  various  movements  of  the  body  are  effected. 
They  possess  the  property  of  contractility  and  are  the  active 
organs  of  locomotion.  Muscular  tissue  is  divided  into  two 
varieties.  Striated  and  Non-striated.  They  may  be  dis- 
tinguished from  each  otlier — 1st.  By  their  color;  the 
striated  are  reddish  in  color,  while  the  nonstriated  are  pale. 
2nd.  By  the  aid  of  a  microscope ;  the  striated  muscular 
fibres  are  characterized  by  being  marked  with  transverse 
lines  or  striae ;  other  stria3  pass  longitudinally,  indicating 
the  direction  of  the  fibrilhie.  The  nonstriated  muscular  tis- 
sue consists  of  pale-colored  fusiform  fibre  cells.  3rd.  By 
galvanism.  The  striated  respond  to  galvanism  instantly, 
by  a  clonic  spasm,  while  the  nonstriated  respond  slowly  by 
a  tonic  spasm.  Muscular  tissue  is  also  divided  into  volun- 
tary and  involuntary,  according  as  it  is  under  the  control 
of  the  will,  or  independent  of  it. 

Striated. — This  variety  of  muscular  tissue  comprises  the 
whole  of  the  voluntary  muscles,  the  diaphragm,  muscles  of 
the  ear,  tongue,  pharynx,  upper  part  of  the  a^sophagus, 
heart,  and  the  veins,  at  their  entrance  to  the  heart.     When 


c 

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TISSUES. 


a  transverse  section  of  a  muscle,  as  the  sartor iiis,  is  examined 
by  the  microscope,  it  appears  to  be  formed  of  a  number  of 
large  bundles  of  muscular  tissue,  enclosed  in  a  coat  of  areo- 
lar tissue,  which  constitutes  the  sheath  or  perimysiuin  ex- 
ternum of  the  muscle.  Each  larger  bundle  consists  of  nu- 
merous smaller  ones,  enclosed  in  a  similar  covering  of  con- 
nective tissue,  called  the  perimysium  internum.  Each 
smaller  bundle  contains  tlie  priTnitive  fasciculi  or  fibres, 
and  cfch  primitive  fibre  contains  the  primitive  Jibrillce. 

In  the  spaces  between  the  bundles  may  be  seen  the  ves- 
sels and  nerves  for  the  supply  of  the  tissue. 

The  Primitive  Fasciculi  or  Fibres. — Each  primitive 
fibre  contains  a  number  of  primitive  fibrillae,  and  is  sur- 
rounded by  a  sheath  of  transparent  homogeneous  membrane, 
the  myolemma  or  sarcolemma.  Resting  upon,  and  sometimes 
beneath  this  membrane  may  be  found  here  and  there,  oval 
nuclei  surrounded  by  a  small  quantity  of  protoplasm.  Thr 
primitive  fibres  are  cylindrical  or  prismatic  in  shape,  and 
vary  in  thickness  from  j}-j^  to  ^  J  „^  of  an  inch  (125  to  50  mmm) ; 
their  length  does  not  exceed  on  an  average  one  inch  and  a 
half.  They  are  marked  by  fine,  dark,  wavy,  or  curved 
^'t'-  '^*-  parallel   lines   or  stride,  from 

TuAoo  to  T70TJO  of  an  inch 
apart(2.5to  2.12mmm), which 
pass  trans  versely  around  them; 
this  is  characteristic  of  this 
i|i)  variety  of  muscular  tissue. 
Other  ]ines,  less  distinct,  run 

Muscular  fibre  torn  across;  the  sarcolemma    Innrrif  nrlinnll  v   inrl  ion  Hn<r  Hip 
still  coniiectiiijf  the  two  piirts  of  the  fibres.        lOngHUCUnaiiy,  inUlCating  tue 

direction  of  tlie  fibrillpe  of  which  the  fibre  is  composed. 
They  have  a  tendency  to  split  both  in  a  transverse  and 
longitudinal  direction,  but  cohesion  is  greatest  in  the  former 
•direction.  . 

The  Primitive  Fibrill.*:. — These  constitute  the  proper 
.contractile  tissue  of  the  muscle.  They  are  cylindrical  or 
prismatic,   sometimes  fiatteued — depending  on  pressure — 


MUSCLE. 


85 


vary  iu  thickness  from  tootjo  ^^  ttiotttt  of  an  inch  (2.5  to  1.4 
mnini.),  and  are  marked  by  transverse  strife  with  which 
those  on  the  surface  of  the  fasciculi  correspond.  Each 
fibrilla  consists  of  a  single  row  of  minute  par- 
ticles, named  "  sarcous  elements,"  connected 
together  like  a  string  of  beads.  When  ex- 
amined by  the  micro.«cope  the  sarcous  elements 
present  a  rectangular  outline,  and  the  fibrilh^ 
appear  to  consist  of  light  and  dark  particles 
or  zones  placed  alternately  ;  hence  their  stri- 
ated appearance.  The  dark  particles  corres- 
pond with  the  sarcous  elements,  and  the  light 
ones  with  the  junction  of  the  pairs.  They  some- 
what resemble  a  Volta's  pile.  The  transverse 
stria3,  vary  from  TxroiTTr  to  Taioo  of  an  inch 
apart  in  the  human  subject ;  in  birds  totoo»  ^^ 


Fil)rillii!     niagni' 

reptiles  t^^-t,  in  fish  ^rrrr:,  and    in   insects  fled  soo  diameters ' 
_I 

8  A  00 


a,  a,   larjfer,  and  1>, 

b,  sinallet'  liuiidles ; 

c,  still   Minallcr  ;  d, 

d,  the  smallest  re- 
presenting; a  sini^Ie 
series  of  sarcous 
elements(Shaq)ey). 


of  an  inch,  (2  to  3  mmm.)  When 
examined  with  a  high  magnifying  power, 
a  dark  line,  with  granules  above  and  below,  is 
seen  to  cross  the  middle  of  each  light  particle,  known  as 
Krause's  transverse  lines  or  intermediate  discs.  The  granu- 
lar appearances  above  and  below,  are  called  secondary  discs. 
A  white  line  has  also  been  observed  to  cross  the  middle  of 
the  dark  zones,  known  as  Hensen's  median  disc.  Late  re- 
searches have  also  shown  that  each  fibrilla  is  surrounded  by 
an  extremely  thin  membrane.  This  is  an  argument  iu  favor 
of  the  view,  that  the  fibrilla  is  the  anatomical  element  of 
muscular  tissue.  The  striated  muscle  of  the  tongue  and 
heart  of  the  mammalia  and  man,  is  somewhat  di  fie  rent  from 
that  generally  met  with.  The  fibres  are  not  arranged  in 
bundles,  and  surrounded  by  connective  tissue,  but  weave  or 
interlace  among  each  otiier.  They  also  anastomose  with 
each  other,  so  as  to  I'orm  a  narrow-meshed  net  work,  and 
there  is  no  appearance  of  sarcolennna. 

NoNSTRiATED. — This  variety  consists  of  flattened  bands, 


c 


mof 

r 

i* 

B" 

»v 

•w 

•at 

1 

9va 

f 

IVf 

r. 


86 


TISSUES. 


or  elongated  fusiform  fibre-cells,  of  a  pale  color,  from  — i—  to 


to  j^^  of  an  incli  (5.5  to  7.5  mmm)  broad, finely  granular  and 
containiiig  a  rod-shaped  nucleus,  which  sometimes  appears 
as  a  streak  (Fig.  36).  These  fibre-cells  may  a.ssume  differ- 
ent shapes  ;  thoy  are  generally  fusiform,  but  some  are  club- 
shaped,  and  others  of  a  rectangular  shape,  with  fringed  ex- 
Fig.  30.  tremities.  The  length  of  these  fibre-cells  is 
from  ^L.  to  —J—  of  an  inch  (500  to  2.5  mmm.) 

ft  O  1  O  O  O  ^  ^  ' 

They  are  held  together  by  connective  tissue, 
and  the  bands  are  applied  to  each  other  in  such 
a  way,  as  to  encircle  the  organ  into  the  form- 
ation of  which  they  enter.  This  kind  of  tis- 
sue is  found  in  all  hollow  organs  (except  the 
heart  and  veins  attached),  as  the  ducts  of  the 
salivary  glands,  tracliea  and  br«  nchi,  alimen- 
tary canal,  fiom  the  lower  part  of  the  oesoph- 
agus to  the  internal  sphincter,  gall  bladder 
and  ducts,  calyces  and  pelvis  of  the  kidney, 
ureters  and  bladder,  and  in  the  urethra.  In 
the  female ;  in  the  vagina,  uterus,  Fallopian 
tubes  and  round  ligaments.  In  the  male;  in 
the  scrotum, epididymuSjVas  deferens,  vesiculse 
seminales,  prostate  and  cavernous  bodies,  in 
the  coats  of  arteries,  veins  and  lymphatics  ;  in 
the  iris  and  ciliary  muscle,  and  in  the  integu- 
ment called  the  arrectores  piloruini. 

Mode  of  Development. — There  is  no  differ- 
ence in  the  early  stage  of  development  between 
the  striated  and  nonstriated  varieties  of  muscular  tissue,  both 
being  developed  from  cells; but  whilst  the  striated  variety 
goes  on  to  complete  development  into  fibrill8e,the  nonstriated 
retains  permanently  its  cellular  condition.  The  cellular  ele- 
ments are  elongated  and  applied  end  to  end,being  held  together 
by  connective  tissue,  and  in  this  way  they  encircle  the  organ 
into  the  formation  of  which  the}'^  enter,  or  are  arranged  longi- 
tudinally or  obliquely.     The  striated  fibre  is  not  formed  as 


Nonstriated  mus- 
cular fibre  cells. 
a,  Developiii)?  cell 
from  the  embryo 
of  the  hoK  ;  b,  a 
more  advanced  cell, 
c,  to  fi-,  various 
forms  of  human 
muscular  fibre. 


MUSCLE. 


87 


Fiff.  37. 


formerly  supposed  by  Schwann,  directly  from  the  arrange- 
ment and  fusion  of  the  cells  in  a  linear  manner  (except 
probably  the  fibres  of  the  heartj,  but  by  the  arrangement 
and  fibrillation  of  the  protoplasm  or  intercellular  substance 
under  the  influence  of  the  cells.  The  cells  appear  to  increase 
greatly  in  length,  the  nuclei  increase  in  number,  and  the 
protoplasm  and  intercellular  substance  becoine  transformed 
into  the  sarcous  elements,  etc.  The  fibre  becomes  trans- 
versely and  longitudially  stiiated,  and  increases  in  size  by 
fresh  additions  of  protoplasm  upon  the  outside.  The  re- 
mains of  the  nuclei,  surrounded  by  granular  protoplasm 
(the  muscle  corpuscle)  may  be  seen  on  the  outside  and  with- 
in the  sarcolemma,  on  the  addition  of  a  little  acetic  acid. 

Attachment  of  Tendons, — Every  muscle  is  attached  at 
its  extremity  by  means  of  connective  tissue,  which  consti- 
tutes the  tendon.  The  extremity 
of  each  muscular  fibre,  whether 
rounded,  pointed,  or  irregular,  is 
covered  by  sarcolemma,  and  is  re- 
ceived into  a  corresponding  cavity 
in  the  tendinous  bundle  to  which  it 
is  firmly  connected,  by  means  of  a 
cement  substance.     This  union   is        Extrcniity  of  imiscuiar  fibru, 

PIT  showing  the  uttiichineiit  of  the  teii- 

so  firm,  that  ru[)ture  of  the  tendon  don. 
or  muscle  will  take  place  before  separation  at  this  point. 
It  may  be  separated  for  microscopical  examination,  by  means 
of  a  solution  of  potash. 

Chemical    Constituents. — Muscular  tissue  consists  as 
follows  in  100  parts  : 

Water - 76. 50. 

Myosine,  Albuminous  substances  and  Hemoglobine..  18.20. 

Lactic  acid '.    i.oo. 

Gelatine 1.50. 

Creatine,  Extractive,  and  Fatty  Matter  and  Salts. .  . .   2.80. 


100.00. 


c. 


vr. 

V 


It  swells  out  on  the  addition  of  acetic  acid,  and  is  par- 
tially dissolved.     It  is  soluble  in  hydrochloric  acid,  and  is 


88 


TISSUES. 


precipitated  by  forronyauide  of  iron.  Muscular  tissues  is 
sometimes  changed  into  a  substance  called  adipocere.  (See 
oils  and  fats.) 

Vascular  Supply. — The  arteries  intended  for  the  supply 
of  the  muscle  pierce  the  sheath,  and  divide  and  subdivide, 
giving  off  small  branches  which  pass  between  the  bundles 
of  which  it  is  com])osed,  until  the  ultimate  twigs  insinuate 
themselves  between  the  primitive  fasciculi  or  fibres,  and 
terminate  in  the  capillaries.  Some  of  these,  the  longitudinal, 
course  along  the  fibres,  lying  in  the  intervals  between  them, 
and  others  pass  transversely  across  them.  The  length  of 
the  longitudinal  capillaries  is  about  Vtr  of  an  inch  (1.2  mm) 
the  transverse  vary  according  to  the  size  of  the  fibres.  The 
fibrillin  are,  therefore,  supplied  by  imbibition  through  the 
sarcolemma. 

Nervous  Supply. — The  nerve  fibres  are  distributed  sim- 
ilarly to  the  arteries,  until  the  filaments  reach  the  fasciculi 
or  fibres.  Tiiey  then  form  a  scries  of  loop.s,  which  either 
return  to  the  same  trunk,  or  join  an  adjacent  one.  It  is 
stated  by  some  observers,  that  the  nerve  fibres  pierce  the 
sarcolemma.  As  they  })ierce  the  fibre,  their  covering  be- 
comes continuous  with  the  sarcolemma,  and  the  axis  cylin- 
I'i;.^:*^-  der  or  essential  portion  of  the  nerves 

l)ass  into  the  interior  and  are  dis- 
tributed among  the  fibrillre,  and  ter- 
minate either  in  free  extremities,, 
loops,  or  neive  buds  (as  they  are 
called). 

Accord injx  to  other  observers  the 
nerve  fibres  as  they  approach  the 
sarcolemma  form  expansions,  called 
terminal,  or  motor  end  plates.  The 
sheath  of  the  nerve  spreads  out  and  blends  with  the  sar- 
colemma, the  white  substance  of  Schwann  terminates  ab- 
ruptly, and  the  axis  cylinder  spreads  out  beneath  the  sar- 
colemma on  the  fciirface  of  the  fibrillse,   forming  an  oval 


^^HQ90 


Terniinatioii  <if  a  nnve  fibre 
by  a  motor  end  plate  in  muscu- 
ar  fibre,  (LonKct). 


MUSCLE. 


81> 


j_    to  -J  - 

A  O  O  1  0  0  o 


of  an  inch  (50  to  25  mmm)  in  diara- 


plate,  from 
eter.     (Fig.  38). 

Properties  of  Muscular  Tissue. — The  di.stinguishing 
characteristic  of  muscular  tissue  is  its  property  of  contrac- 
tility, irritability  or  tonicity.     Some  have  endeavoured  to- 
draw  a  distinction  between  these  teims  ;  but,  after  all,  it  is 
a  distinction  without  a  ditference.     The  term  tonicity  how- 
ever, may   be  understood   to   express  that  hueni'^ible  and 
almost   constant   contraction   by   which  opposing  mu.scles 
balance  each  other  in  a  state  of  rest — a  state  of  passive  con- 
traction.    The  primitive  fibril  la    is  the  proper  contractile 
tissue  of  the  muscle.     Still,   it   is  a  disputed  point  as  to 
whether  or  not  it  possesses  this   property  in  itself,  some 
maintaining  that  nerve  is  neces.sary  to  charge  it  with  con- 
tractility ;  others  that  nerve  is  only  necessary  to  call  it  into- 
action,  and  that  this  ])roperty  is  inherent  in  the  tissue  itself. 
Contraction  is  caused  by  a  change  in  the  shape  of  the  sar- 
cous   elements;    they  become   shorter  and   thicker.     This 
change  travels  rapidly  fi-om  one  end  of  the  JihriUa  to  the 
other,  and  the  muscle  is  thus  very  much  shortened.     Some 
vegetable  structures  possess  an   analogous  property,  as  e.  g. 
the  mimosa  or  sensitive  plant,  and  venus'  fly-trap  (Dionoea). 
If  touched  ever  so  slightly,  the  irritation  causes  a  change  in 
the  shape  of  the  cells,  followed  by  a  change  in  the  shape  or 
position  of  the  v^hole  leaf,  in  consequence   of  the  change 
travelling  from  one  cell   to  another.     The  property,  there- 
fore, of  contractility  is  inherent  in  the  muscular  fibrilla 
itself,  and  may  be  called  into  action  by  various  kinds  of 
stimuli,  as  by  nervous   influence,  by  pinching  or  pricking 
the  tissue,  by  the  action  of  an  acid  or  an  alkali,  or  by  gal- 
vanism.  The  efiect  of  the  application  of  any  of  these  stimuli,, 
varies  according  to  the  kind  of  muscular  tissue  to  which  it 
is  applied.     If  a   portion   of  striated  muscle  be  irritated, 
those  fibres  which  are  touched  will  contract,  and  those  only,, 
the  motion  not  being  communicated  to  any  other,  and  the 
contracted  part  soon  becomes  relaxed — the  spasm  is  clonic. 


c 

c 

Mtl> 

r 

R, 

h 

»»L 

•w 

m\ 

mKi 

1 

t 

■1 
.4 

■ft 

1 

rt 

fnv 

1 

f.  ■ 

1 
J 

^'■• 

r.. 

V 

90 


TISSUES. 


If,  on  the  other  hand,  a  portion  of  nonstriated  muscle  be 
irritated,  as  the  alimentary  canal,  the  contraction  takes 
place  more  slowly,  the  spasm  is  long  continued,  or  tonic, 
and  the  movement  is  communicated  to  other  fibre-cells, 
until  a  considerable  part  of  the  canal  is  affected.  The 
muscular  fibre  is  shortened  and  thickened  during  contrac- 
tion, and  sometimes  thrown  into  a  zigzag  shaj)o,  and  som(j 
observers,  mistaking  the  effect  for  the  cause,  cijncluded  that 
the  zigzags  occasioned  the  shortening.  Contractility  con- 
tinues for  a  short  time  after  death  This  may  be  demon- 
strated, by  applying  to  the  muscular  tissue  any  of  the  above- 
mentioned  stimuli  which  arc  known  to  affect  it  during  life. 
The  duration  of  this  property  after  death,  varies  in  different 
animals.  In  birds,  only  a  few  minutes  after  death ;  in 
quadrupeds  much  longer ;  while  in  reptiles  it  remains  for 
many  hours,  owing  to  the  nutritive  changes  being  more 
sluggish  in  these  than  in  warm-bloods,  and  the  sareuus  ele- 
ments being  slowly  formed  and  sluggish  in  their  action,  are 
long-lived. 

If  irritation  be  continued,  the  contractility  or  irritability 
of  the  n\uscle  is  soon  exhausted.  The  circulation  of  arterial 
or  oxygenated  blood  is  not  only  necessary  for  the  purjjoses 
of  nutrition,  but  also  to  the  continuance  of  contractility. 
The  muscles  will  therefore  preserve  their  contractility  after 
death,  and  the  action  of  the  heart  itself  will  continue  for  a 
long  time,  if  oxygenated  blood  be  injected  into  the  veins  or 
if  the  circulation  be  kept  up  by  artificial  respiration.  If  the 
blood  be  charged  with  carbonic  acid,  or  chloroform,  ether, 
sulphocyanide  of  potassium,  or  a  narcotic  poison,  as  opium, 
etc.,  the  contractility  of  the  muscles  is  speedily  destroyed. 

Every  act  of  contraction  involves  the  death  of  a  certain 
amount  of  muscular  tissue,  and  prolonged  exertion  causes 
fatigue,  which  is  an  evidence  of  an  impaired  condition. 
Rest  is  necessary  to  I'ecovery,  and  recovery  is  due  to  the 
nutritive  process ;  hence  the  more  a  muscle  is  used,  pro- 
vided it  receives  a  sufficient  amount  of  rest  and  nutrition, 


MUSCLE. 


91 


tlie  more  vigorous  and  bulky  does  it  bocomo  ;  as  v..  g.,  the 
arm  of  the  smitli,  and  the  lcf(s  of  the  rope-walker.  On  the 
other  hand,  disease,  as  paralysis,  or  sedentary  liabits,  cause 
thorn  to  become  flabby  and  atrophied,  but  this  may  be  re- 
medied by  exercise,  and  the  use  of  friction  and  galvanism. 
In  some  constitutions  they  are  liable  to  fatty  degeneration. 

Muscular  coiitraction  produces  a  Hound  resembling  the 
distant  rumbling  of  carriage  wheels.  This  is  caused  by  the 
movements  of  the  fibres  U])on  each  other.  For  example,  the 
sound  caused  by  the  contraction  of  the  masseter  and  tem- 
poral muscles  may  be  distinctly  heard  in  the  stillness  of  the 
night,  by  placing  the  side  of  the  face  and  ear  on  the  pillow, 
and  clenching  the  teeth  fiimly  together. 

There  is  also  an  elevation  of  femperatitre  of  from  1°  to  2° 
F.  This  depend-^  ])artly  on  the  chemical  changes  which 
take  ])lac'3  in  tlie  muscle,  as  a  result  of  its  action,  and  partly 
upon  the  friction  consequent  on  the  movements  of  the  fibres 
upon  each  other. 

Muscular  tissue  is  also  said  to  possess  a  certain  amount 
of  elasticity/.  This  is  exceedingly  small,  and  is  due  in  great 
measuie  to  the  elasticity  of  the  sarcolcmma  and  the  elastic 
tis.sue  associated  with  muscle.  It  is  sh')wn  by  suspend- 
ing vertically  a  small  weight  to  a  |)ortion  of  fresh  muscle  ; 
it  elongates  with  the  weight  and  recovers  itself  when  it  is 
removed. 

Rigor  Mortis. — This  is  the  stiffening  of  the  muscles 
which  takes  place  after  death,  and  is  due  to  the  coagulation 
of  myosin.  This  condition  is  rarely  absent  ;  but  it  may  be 
very  slight,  and  continue  only  a  short  time.  Sometimes  it 
comes  on  within  15  or  20  minutes  after  death,  as  in  typhus 
fever.  It  commonly  takes  place  within  7  or  8  hours  after 
death ;  but  in  some  cases  it  may  be  deferred  for  20  or  30 
hours.  It  continues  for  2-t  or  SC  hours  ;  but  it  may  ])ass 
off  much  more  rapidly,  or  be  continued  for  several  d  lys. 
This  rigor  mortis  is  a  sort  of  tonic  contraction  of  the  mus- 
cles, and  in  some  cases  it  may  be  very  violent — as  afcer 
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TISSUES. 


death  from  cholera  and  yellow  fever — and  has  given  rise  to 
many  absurd  superstitions  among  the  uninitiated.  It  begins 
in  the  neck  and  lower  jaw  first,  next  the  upper  extremi- 
ties, and  extends  from  above  downwards  until  it  reaches 
the  lower  limbs.  It  is  most  remarkably  manifested  in  the 
nonstriated  muscular  tissue,  as  in  the  arteries  and  alimen- 
tary canal.  In  consequence  of  this  contraction,  the  bowels 
are  not  unfrequently  moved  after  death  ;  the  arteries  are 
found  empty,  and  so  contracted  that  they  cannot  be  injected 
until  the  rigidity  passes  off.  When  the  rigor  mortis  sub- 
sides, decomposition  of  the  muscular  tissue  begins ;  hence 
we  may  regard  it  as  the  last  act  of  life,  and  in  this  respect 
it  corresponds  to  the  coagulation  of  the  blood,  when  drawn 
from  the  body.  The  same  causes  that  interfere  with  the 
coagulation  of  the  blood  after  death,  interfere,  al.^o,  with  the 
rigor  mortis  of  the  muscles,  as  in  animals  hunted  to  death, 
or  killed  by  lightning,  in  which  both  coagulation  and  rigor 
mortis  are  imperfect. 

Action  of  Muscles. — In  the  action  of  most  muscles,  and 
especially  those  of  the  extremities,  examples  of  the  three 
orders  of  levers  are  afforded. 

In  the  first  order  of  levers  the  power  is  at  one  end,  the 
weijrht  at  tne  other,  and  the  fulcrum  between  the  two. 

In  the  second  order,  the  power  is  at  one  end,  the  fulcrum 
at  the  other,  and  the  weight  between  the  two. 

In  the  tldrd  order,  the  fulcrum  is  at  one  end,  the  weight 
at  the  other,  and  the  power  between  the  two. 

The  first  order  of  levers,  although  the  most  powerful,  is 
that  least  used  in  the  animal  economy,  as  its  use  is  less  pro- 
ductive of  extensive  motion.  The  action  of  the  gastrocne- 
mius muscle  affords  an  e:.ample  of  this  order,  as  when  the 
foot  is  raised  from  the  ground,  and  extended  to  raise  the  os 
calcis  and  depress  the  toes  :  here  the  moving  power  is  the 
gastrocnemius  attached  to  the  os  calcis,  the  weight  is  the 
anterior  part  of  the  foot,  and  the  fulcrum  is  the  ankle  joint. 
The  same  muscle  affords  an  example  of  the  second  order 


ofh 
bod 


the 


MUSCLE. 


98 


of  levers,  as  when  the  foot  is  placed  on  the  ground  and  the 
body  raised  by  the  action  of  the  muscle  ;  here  the  moving 
power  is  the  gastrocnemius,  the  fulcrum  the  anterior  part  of 
the  foot  resting  on  the  ground,  and  the  weight  or  resistance 
the  body  resting  on  the  ankle  joint. 


Fijf .  39. 


Fig.  40. 


Figr.  41. 


tr 


The  upper  three  flsrures  represent  the  three  kinds  of  levers ;  ',he  first  illustratingf  the 
mode  of  action  in  two  directions.  The  lower  flgur  represent  t'ne  foot  when  it  takes  the 
character  of  each  kind  of  lever.  F,  fulcrum;  P.  -wer;  W,  weight  or  resistance;  M, 
muscle,  affording  the  power. 

The  ankle  joint  also  affords  an  example  of  the  third  order 
of  levers,  as  when  the  foot  is  raised  from  the  ground  and 
flexed  on  the  ankle  joint ;  here  the  moving  pov  er  is  the 
tibialis  anticus  and  peroneus  tertius,  the  fulcrum  is  the 
ankle  joint,  and  the  weight  the  anterior  part  of  the  foot. 

The  biceps  of  the  arm  also  affords  a  good  example  of  the 
third  order,  as  when  a  ball  or  weight  is  placed  in  the  hand  \ 
here  the  moving  power  is  the  biceps  inserted  into  the  tuber- 
osity of  the  radius,  the  fulcrum  is  the  elbow  joint,  and  the 
weight  is  in  the  hand  In  this  position,  power  is  sacrificed 
to  extent  of  motion,  as  in  raising  the  hand  and  weight  these 
pass  through  the  arc  of  a  circle  of  considerable  dimensions, 
while  the  extent  of  motion  at  the  insertion  of  the  power  is 
extremely  limited.  This  is  still  more  obvious  when  we 
hold  a  rod  in  the  hand,  as  a  fishing-rod  or  whip,  the  ex- 
treme end  of  which  is  made  to  pass  through  a  space  of  con 
siderable  magnitude  compared  with  that  of  the  part  where 


Uxui 

*- , 


P 


'SSUES 


the  power  is  app-ied.  The  great  advantage  derived  from 
this  disposition  of  levers  in  the  hun^_an  body,  whereby 
motion  is  gained  at  the  expense  of  power,  is  seen  in  the 
various  acts  of  walking,  running,  leaping,  etc. 

Locomotion. — In  the  act  of  walking  nearly  every  muscle 
in  the  body  is  called  into  action,  either  in  the  movement  of 
the  limbs  or  in  the  maintenar.ee  of  the  body  in  the  erect 
position.  Two  main  kinds  of  leverage  are  employed  in 
walking,  one  kind  chiefly  produced  by  the  muscles  of  the 
calf  which  raise  the  heel,  and  with  it  the  weight  of  the 
body  which  is  inished  forward,  and  would  fall  prostrate,  but 
for  the  other  kind  of  leverage  by  which  the  opposite  leg  is 
pulled  or  planted  in  front  of  the  body  to  support  it.  The 
advance  of  the  opposite  leg  is  effected  })artly  by  swinging, 
but  chiefly  by  muscular  action.  The  muscles  concerned  are 
those  of  the  thigh,  the  rectus,  psoas  and  iliacus,  which  act  in 
front;  the  hamstring  muscles  which  slightly  bend  the  knee, 
and  those  on  the  front  of  the  leg,  as  the  tibialis  anticus, 
extensor  longus  digitorum,  extensor  longus  pollicis  and  per- 
oneus  tertius  which  raise  the  foot  and  toes,  and  prevent 
them  catching  on  the  ground.  When  this  foot,  which  we 
will  suppose  to  be  the  rigid,  has  reached  the  ground,  the 
action  of  the  muscles  of  the  left  leg  has  not  ceased,  but  con- 
tinues to  raise  the  heel  and  throw  the  body  still  more  for- 
ward, until  the  weight  is  supported  by  the  right  leg,  when 
the  left  in  its  turn  swings  around  and  is  planted  in  front 
of  the  body.  The  two  actions  it  will  be  seen,  therefore,  are 
taking  place  at  the  same  time,  and  are  assisting  each  other. 

At  the  same  tin.j  that  the  above  movements  are  in  pro- 
gress, the  body  i ,  being  supported  in  the  erect  posture  and 
balanced  on  each  leg  alter;  itely.  This  is  done  by  a  slight 
rotation  of  the  pelvis  on  the  head  of  each  femur  alternately, 
so  that  the  centre  of  gravity  Cx''  the  body  shall  fall  over  the 
foot  of  that  side.  This  occasions  a  sliti'ht  "  rockinc:  move- 
ment"  which  is  more  noticeable  in  females  than  males  owing 
to  the  greater  width  of  pelvis  of  the  former.     Tins  rockicg 


MUSCLE. 


95 


movement  may,  however,  be  lessened,  and  made  more  grace- 
ful by  a  compensatory  outward  movement  at  the  hip,  and 
hence  some  may  become  more  graceful  in  their  walk  than 
others.  Running,  and  leaping  or  jumping  are  modifications 
of  the  act  of  walking. 

In  regard  to  the  source  of  muscular  force,  it  has  long 
been  observed  that  in  active  muscular  exercise,  there  is  an 
increase  in  the  urea  excreted  by  the  kidneys,  and  it  was 
supposed  that  this  increase  of  urea  was  in  exact  proportion 
to  the  amount  of  muscular  exercise.  The  latter  has  been 
found  not  to  be  the  case  ;  the  increase  in  urea  is  only  very 
slight,  and  the  waste  of  muscle  cannot  be  expressed  by  its 
increased  excietion;  neither  is  the  substance  of  muscle 
wasted  in  proportion  to  the  work  it  performs.  There  is  also 
no  evidence  that  nitrogenous  are  superior  to  non-nitrogenous 
foods  as  a  source  of  muscular  power ;  both  may  afford  the 
requisite  conditions  for  muscular  action. 


c 

v*  •-■ 


« ' 


4 
1 


I. 


90 


MEAfBRANOUS  EXPANSIONS. 


CHAPTER  IV. 


MEMBRANOUS   EXPANSIONS. 

These  are  the  serous  and  synovial,  mucous  and  integu- 
fnent.  The  serous  and  synovial  membranes,  anatomically 
speaking,  form  shut  sacs,  with  the  exception  of  the  periton- 
eum in  the  female,  which  communicates  with  the  uterus 
through  the  Fallopian  tubes.  The  mucous  membrane  lines 
cavities  which  communicate  with  the  external  surface,  and 
is  continuous  with  the  integument.  The  integument  covers 
the  exterior  of  the  body,  and  serves  not  only  as  a  means  of 
protection,  but  also  as  an  organ  of  sensation.  The  mucous 
membrane  and  integument  are  convertible  membranes. 

Structure. — The  structure  of  these  membranes  is  very 
nearly  the  same  in  each  instance.  It  consists  of  a  base- 
ment membrane,  lined  by  epithelial  cells  on  the  free  sur- 
face, and  presents  vessels,  nerves,  and  lymphatics,  imbed- 
Fijf.  i-2. A^^  jjj  areolar  tissue  which 

connectsitwiththe  subjacent 

parts  (Fig.  42).    They  there- 

I  fore  consist  of  three  parts — 

\hasement    membrane,  with 

\epithelial  cells  or  one  side, 

Plan  of  a  membranous  expansion  ;  a.epithe-  .,  i  hlnnd-iwavfils  'nt>TiWRS\T\^ 
Hum  ,  b,  basement  membrane  ;  c,  vessels,  ^"<1  OlOOa  VCSSClS,  ncrveS  anu 
nerves  and  lymphatics  imbedded  In  areolar  ^^^^^^^-^^^  imbedded  in  ar- 
eolar tissue,  on  the  other. 

1st.  Basement  Membrane. — The  different  varieties  of 
basement  membrane  have  been  already  described  in  Chap- 
ter II.  Its  function  is  to  support  the  cells,  and  probably 
influence  their  development ;  to  limit  osmosis  of  the  nutri- 
ent fluid  from  the  subjacent  capillaries,  and  modify  it  in 
its  passage. 

2nd.  Epithelium. — The  layer  of  cells  which  line  the  free 


m 


EPITHELIUM. 


97 


surface  of  tlse  membranous  expansions,  is  called  epithelium. 
Those  which  line  the  serous  and  synovial  me'^ibranea  and 
the  vascular  system  are  sometimes  called  endofhelium,  and 
the  striitified  epithelium  of  the  skin  is  called  epidermis. 
The  epithelial  celh  can  be  brought  beautifully  into  view 
by  staining  with  nitrate  of  silver. 

There  are  two  principal  varieties  of  epithelium,  viz  :  Ist. 
Tesselated,  pavement,  squamous,  laminated  or  scaly.  2nd. 
Columnar  or  cylindrical.  In  the  serous,  synovial,  and 
mucous  membranes  there  is  generally  a  single  layer  of  cells, 
Avith  a  quantity  of  granular  matter  and  a  layer  of  partially 
developed  cells  lying  on  the  basement  memb  'ane  ;  l)ut  in 
the  integument  there  are  several ;  the  outer  being  flattened, 
scaly,  and  hardened  by  secondary  deposit.  The  cells  which 
line  the  serous,  synovial  and  nuicous  membranes,  secrete  a 
fluid  which  is  intended  to  lubricate  the  surface,  to  prevent 
the  ill  effects  of  friction,  and  to  give  ease  to  the  gliding 
movements  of  the  parts  over  each  other.  This  fluid  is 
formed  as  a  result  of  the  growth,  maturity,  and  decay  of  the 
cells. 

1st.  Tesselated,  Pavement,  Squamous,  or  Scaly  Epi- 
thelium.— The  cells  of  this  variety  are  flattened  and  poly- 
gonal in  shape,  and  vary  in  size  from  <,Iq  to  ^^ir.  of  an  inch 
(50  to  10  mmm)  in  diameter.  Each  cell  contains  a  nucleus, 
nucleolus,  and  granular  matter.  They  are,  in  general,  not 
very  active,  and  are  therefore  long-lived.  In  health,  they 
secrete  only  a  limited  quantity  of  fluid.  Those  which  line 
Fig.  43.  the    synovial   membranes,  mucous 

membrane  of  the  mouth,  and  parts 
of  the  body  in  which  a  greater  sup- 
ply of  fluid  is  requisite,  are  some- 
what rounded  in  shape  and  much 
more  active.  Tesselated  or  pave- 
ment epithelium  lines  all  the  serous 


a,  epith 
peri 
epithelial  cell  of  the  mouth  x   2G0 


Tesselated  epithelium ;  a,  epim-  ,  .    ,  .  ,, 

eiium  of  the  peritoneum  x  400 ;  b,  and  syuovial  membranes,  the  mu- 


(fienie).  cous  membrane  oi  tlie  mouth,  lower 

part  of  the  pharynx,  oesophagus,  upper  part  of  the  larynx, 


c 

ttn» 

If ' 
«■ 


1 . . 


98 


MEM li RANG  US  EXPANSIONS. 


Kijf.  44. 


intercellular  passages  (so  called),  and  air  cells,  lining  mem- 
brane of  the  ventricles  ot*  the  brain,  tympanum,  anterior 
and  posterior  chambers  of  the  eye,  conjunctiva  and  canali- 
culi,  arteries,  veins,  and  lymphatics,  lower  part  of  the 
vagina,  bladder,  and  urinary  passages,  vesiculte  seminales, 
and  vas  deferens. 

Those  cells  which  line  the  bladder  and  urinary  passages 
are  somewhat  sj)heroi(lal  in  shajie,  and  would  seem  to  bean 
intermediate  variety. 

2nd.    COLUMNAK     OR    CYLINDRICAL    EPITHELIUM. —    This 

variety  is  cylindrical  in  shape,  as  the  name  indicates,  and 
placed  side  by  side,  one  extiemity  of  the  cell  resting  on  the 
basement  membrane,  and  the  other  forming  tlie  free  surfac..-. 

They  vary  in  size  from  2.'n«  to  -j-gV,, 
of  an  inch  (10  to  7.1  niumi.)  in  thick- 
ness, and  from  -g  J^  to  ^\-^  of  an  inch 
(42  to  28  mmm.)  in  length.  Each 
cell  contains  a  nucleus  and  nucleolus. 
In  some  parts,  as  in  the  gastro-intes- 
tinal  canal,  there  ai)])ears  to  be  a 
columnar  ci.ithciin.n ;  c,  col-  ^ouble  layer  of  cclls  /  thjs  depends 
=:;ZdS1;m;^u«n/oi  on  their  rapid  development  in  these 
"'"  ""'"^'  parts,  the  lower  layer  being  the  new 

cells  which  are  rising  np  to  take  the  place  of  the  old.  Therje 
cells  not  only  line  the  free  surface  of  the  membrane,  but 
also  dip  into  the  follicles,  at  the  bottom  of  which  they  be- 
come rounded  or  glandular.  This  is  owing  to  their  greater 
activity  in  the  latter  situation.  In  some  instances  their 
free  extremities  are  club-shaped,  in  order  to  comport  with 
their  position,  as  when  they  stand  on  the  angles  formed  by 
the  dipping  of  the  follicles. 

This  form  of  epithelium  is  found  in  the  alimentary  canal, 
commencing  at  the  cardiac  orifice  of  the  stomach,  in  the 
ducts  which  communicate  with  it,  the  gall  bladder,  nose, 
nasal  ducts  and  lachrymal  sacs,  frontal  sinuses  and  antra, 
posterior  surfac3  of  the  palate,  upjier  part  of  the  pharynx. 


CILIA. 


m 


Eustachian  tubes,  larynx — below  the  superior  vocal  cords — 
tiachea  and  bronchi,  uj)per  part  of  the  vagina,  uterus,  and 

Fallopian  tubes. 

Placed  here  and  there  at  vari- 
able distances  among  the  ordinary 
columnar  cells  are  peculiar  oval 
cells  known  as  Becher  or  gubld- 
cells  (Fig.  45,  a.)  These  are  re- 
garded by  some  as  the  commence- 
ment  of  the  absorbent   system  ', 

Coluniiiar  epithelium  of  small  intes-    by  OthcrS  aS  mere  shcUs  of   Cpitll- 
tiiie;  a,  Uucher  or  jfoblet  cells;  b,  or-       ,.    ,  ,,  ,  .    ,        i  i 

(linar.v  cells.  elial    cclls   which    liavc    becom© 

emptied  of  their  contents  by  manipulation,  or  as  mucous 


secreting 


cclls. 


Cilia. — Both  varieties  of  epithelial  cells  occasionally  pre- 
sent a  number  of  minute,  conical-shaped  filaments  or  prolon- 
gations attached  to  their  free  extremities  or  surfaces,  termed 
cilia  (Fig.  44,  d).  They  are  attached  by  their  bases  to  the 
cells,  their  free  extremities  being  tapered,  and  they  vary  in 
length  from  ^o'tjcj  to  ToVfy  of  an  inch,  (5  to  6  mmm.)  From 
five  to  thirteen  may  be  seen  attached  to  each  cell.  The  cilia, 
may  be  considered  as  prohjngations  of  the  cell  itself  They 
are  not  seen  in  the  early  stage  of  development  of  the  cell,  but 
make  their  a])peai"ance  ai  it  arrives  at  maturity.  They  are 
in  continual  motion ;  each  filament  appears  to  bend  from 
its  root  to  its  point  and  return  to  its  original  state,  so  as  to- 
resemble  the  waving  of  a  wheat  field  in  a  gentle  breeze. 
This  motion  is  independent  both  of  the  will  and  the  life  of 
the  animal,  as  it  is  .seen  to  continue  after  death.  Epithelial 
cells  of  the  nose  may  be  seen  to  float  about  in  water  by  the 
agency  of  their  cilia,  several  hours  after  they  have  been  re- 
moved from  the  mucous  surface  ;  and  the  motion  of  the 
cilia  has  also  been  observed  in  the  body  of  the  tortoise  fif- 
teen days  after  death.  Ciliary  motion  continues  in  animals- 
killed  hjr  prussic  acid,  narcotic  or  other  poisons,  and  electri- 
city ;  but  is  destroyed  by  chloroform,  carbonic  acid,  mineral 
acids  and  strong  alkalies. 


it  :. 


?v 


&' 


100 


MEAfliRANOUS  EXPANSIONS. 


The  object  of  the  ciliary  motion  is  to  propel  fluids  over 
the  surface,  in  tlie  direction  which  the  secretion  is  destined 
to  take,  whether  external  or  internal,  the  movement  being 
generally  towards  the  outlets.  In  fishes,  the  external  sur- 
face of  the  gills  is  covered  with  cilia,  which  serve  to  propel 
the  water,  and  bring  fresh  portions  in  contact,  for  the  pur- 
])ose  of  aerating  the  l)lood.  In  raanj'  of  the  lower  animals, 
they  serve  not  only  to  produce  currents  for  respiration,  but 
also  to  draw  into  the  mouth  minute  particles  which  serve 
as  food. 

The  motion  of  the  cilia  is  due  to  the  vitality  of  the  cells 
from  which  they  grow,  or  the  vital  contractility  of  the  tis- 
sue of  the  cilia  themselves,  and  not  to  the  presence  of  a 
kind  of  delicate  muscular  tissue,  or  to  nervous  force,  as  some 
have  suggested.  It  has  already  been  shown,  in  the  preced- 
ing chapter,  that  the  motion  of  muscular  tissue  is  due  to  a 
change  in  the  shape  of  the  sarcous  elements.  Now,  in  the 
same  way,  the  motion  of  the  cilia  may  be  produced  by  a 
change  in  the  shape  of  the  cells  to  which  they  belong,  so 
that  by  an  alternate  contraction  and  relaxation  of  the  cell 
the  cilia  would  be  made  to  wave  as  they  are  seen  to  do. 

The  epithelial  cells  are  developed  from  the  protoplasm 
supplied  by  the  vascular  layer,  beneath  the  basement  mem- 
brane. 

Ciliated  epithelium  of  the  tesselated  or'  squamous  variety 
is  found  in  the  lining  membrane  of  the  ventricles  of  the 
brain,  tympanum,  intercellular  passages  (so  called),  and  in 
the  air  cells. 

Ciliated  epithelium  of  the  columnar  vainety  is  found  in 
the  cavity  of  the  nose  (except  the  roof),  nasal  ducts,  lach- 
rymal sacs,  frontal  sinuses,  maxillary  antra,  Eustachian 
tubes,  posterior  surface  of  the  palate,  upper  part  of  the 
pharynx,  (extending  as  low  down  as  the  floor  of  the  nares), 
larynx  below  the  superior  vocal  cotds,  and  the  anterior  part 
above,  trachea  and  bronchi,  upper  part  of  Uie  vagina,  in  the 
uterus,  and  Fallopian  tubes. 


SEROUS  MEMBRANES. 


101 


SEROUS  MEMBRANES. 

The  serous  membranos  are  the  arachnoid,  pleura,  pericar- 
dium, peritoneum,  tunica  vaginalis,  and  the  lining  membrane 
of  arteries,  veins,  and  lymphatics.  Each  membrane,  respec- 
tively, lines  the  cavity  to  which  it  belongs,  being  attached 
to  the  wall  by  means  of  areolar  tissue.  This  is  called  the 
'parietal  layer.  It  is  then  reflected  upon  the  contained 
organ  forming  the  visceral  layer.  The  free  surface  is  lined 
by  tesselated  or  squamous  epithelium,  sometimes  called 
endothelium,  which  in  health  secretes  a  limited  quantity  of 
fluid  for  the  purpose  of  moistening  the  surface,  the  process 
of  secretion  and  absorption  being  exactly  counterbalanced. 
The  normal  quantity  of  stious  fluid  in  the  various  cavities 
is  as  follows  ;  in  the  pericardium  one  to  two  fluid  drachms ; 
in  the  peritoneum  one  to  three  oimces ;  in  the  pleural  sac 
two  to  four  fluid  drachms.  If  the  secretion  be  morbidly  in- 
creased, or  the  process  of  absorption  diminished  it  is  retained 
in  the  cavity,  and  gives  rise  to  dropsies  which  receive  difler- 
ent  names  in  different  parts  of  the  body ;  in  the  cavity  of 
the  arachnoid,  hydrocephalus  ;  in  the  pleura,  hydrothorax  ; 
in  the  pericardiOra,  hydro-pericardium ;  in  the  peritoneum 
ascites  ;  in  the  tunica  vaginalis,  hydrocele.  The  secetion  is 
called  serous  fluid,  and  is  similar  to  the  serum  of  the  blood. 
It  has  an  alkaline  reactivon,  and  consists  of  water,  albumen 
and  salts.  The  quantity  of  albumen  varies  in  different 
parts,  depending  on  the  activity  of  the  part,  the  degree  of 
motion  and  the  amount  of  friction  to  be  overcome.  In  the 
serous  fluid  of  the  pleura  there  are  2.85  parts  in  a  hundred ; 
in  the  peritoneum,  1.13  parts  ;  in  the  arachnoid,  .6  to  .8;  in 
the  subcutaneous  areolar  tissue,  .36. 

The  rerous  membranes  are  looked  upon  by  some,  as  large 
sacs  or  cavities,  which  communicate  by  stomata  or  pores, 
with  the  lymphatic  vessels  (Klein.)  These  apertures,  which 
are  about  T^Vtro  of  ^^  i^ch  (10  mmm)  in  diameter,  may  be 
seen  between  the  epithelium.     Milk  and  colored  fluids  have 


/It 


I    ■ 


i 

J 


I  .-I 


I' 


102 


MEMBRANOUS  EXPANSIONS. 


been  observed  to  pass  through  them  into  the  lymphatic  sys- 
tem. Short  lateral  passages  of  the  lymphatics  are  also  found 
to  open  into  these  apertures.  There  is  also  a  considerable 
(piantity  of  adenoid  tissue  imbedded  in,  or  forming  the  walls 
of  the  serous  membranes. 


cavn 

the 

tegu 

hllVH 


SYNOVIAL    MEMBRANES. 

The  synovial  membranes  are  ])laced  between  the  articular 
surfaces  of  the  bones.  In  the  foetus  they  are  prolonged 
over  the  articular  cartilage  ;  but  in  the  adult  they  cover 
merely  the  margin  to  the  extent  of  a  line  or  two,  and  are 
then  rertected  on  the  inner  .lurface  of  the  ligaments,  to 
which  they  are  attached  by  areolar  tissue.  In  some  in- 
stances they  send  fringe-lilco  prolongations  into  the  interior 
of  the  joints,  as  for  example,  the  (so  called)  alar  ligaments 
of  the  knee  joint.  They  also  form  sheaths  for  the  tendons 
of  muscles.  The  free  surface  of  the  synovial  membrane  is 
smooth  and  moist,  being  lined  by  a  layer  of  tesselated  or 
squamous  ej)ithelium,  which  secretes  tho  synovia,  for  the 
purpose  of  lubricating  the  joint,  and  preventing  the  ill 
effects  of  friction.  If  the  secretion  be  morbidly  excessive, 
the  result  would  be  hydrops  articidi. 

Synovia  is  a  transparent,  viscid,  oily-looking  fluid,  and 
resembles  the  white  of  an  Qgg,  hence  its  name  {aw,  cum, 
MOV,  ovum.)  It  has  an  alkaline  reaction,  and  contains 
water,  albumen  or  synovine,  and  salts.  It  contains  more 
albumen  than  serous  fluid,  more  being  necessary  on  account 
of  the  greater  amount  of  motion  in  the  joints. 

BuiiSiE. — A  reflection  of  synovial  membrane  in  the  form 
of  a  closed  sac,  is  found  beneath  some  of  the  tendons  where 
they  glide  over  bony  surfaces.  This  is  called  a  synovial 
bursa.  When  they  are  situated  near  a  joint  they  sometimes 
communicate  with  its  synovial  cavity.  They  line  the  canal 
or  groove  and  are  reflected  around  the  tendon  forming  its 
sheath,  at  the  same  time   excluding  it  from  the  synovial 


.S' VA'O VIAL  MEMliRANES. 


103 


cavity.  There  is  nr.other  variety  of  bursjo  situated  between 
the  integument  and  bony  prominences,  as  between  the  in- 
tegument and  patella,  olecranon,  etc.  Tjjcsc  ai-e  called 
h\ir»(M  mrcoscc,  and  are  nothing  more  or  less  than  an  en- 
larged mesh  in  the  areolar  tissue,  surrounded  by  condensed 
fibres,  and  presentirjg  a  partial  or  incomplete  secreting  sur- 
face. 

Synovial  membranes  are  more  readily  reproduced  than 
serous  membranes.  It  is  doubtfid  whether  the  latter  arc 
reproduced  at  all  or  not ;  but  new  joints  are  formed  and 
lined  by  synovial  membrane,  as  is  seen  in  old-standing  dis- 
locations of  the  hip,  etc.  Serous  membi-anes,  vvlien  inflamed 
pour  out  a  plastic  substance,  which  has  a  tendency  to  or- 
ganize and  form  bands ;  but  in  inflammation  of  synovial 
membranes  there  is  a  tendency  to  the  formation  of  j)us. 

Structure  of  Serous  and  Synovial  Membranes. — 
They  are  very  nearly  alike.  On  their  free  surface  is  a 
layer  of  epithelium,  of  a  ])olygonal  shape,  and  more  or  less 
transparent.  This  rests  on  the  basement  membrane,  which 
is  also  nearly  transparent,  and  very  thin.  Beneath  the 
basement  membrane  is  a  layer  of  areolar  tissue,  in  which 
are  imbedded  the  vessels,  nerves  and  lynqjliatics  ;  this  con- 
stitutes the  chief  thickness  of  the  membrane,  and  gives  it 
strength  and  elasticity.  The  areolar  tissue  is  mo''e  con- 
densed beneath  the  brisement  membrane,  and  becomes  more 
lax  near  the  subjacent  tissue.  The  vessels  are  arranged  in 
a  plexiform  manner,  running  parallel  with  the  basement 
membrane.  In  parts  of  the  body  where  there  is  much 
motion,  and  a  greater  supply  of  bloo;l  is  necessary,  as  be- 
nealli  the  pleura  and  the  synovial  membranes,  the  vessels 
are  tortuous. 


c 

*  ■ 

*  ■ 


V 


t* 


MUCOUS   MEMBRANES. 

These  resemble  the  serous  and  synovial,  in  lining  cavities, 
but  they  are  not  shut  sacs.  They  line  the  interior  of  the 
alimentary  canal  from  the   mouth  to  the  anus,  the  ducts, 


104  MEMBRANOUS  EXPANSIONS. 

and  interior  of  glands  which  communicate  with  it;  the  nose 
and  the  passages  which  open  into  it,  the  larynx,  trachea, 
bronchi,  and  air  cells,  bladder  and  urinary  passages,  vagina, 
uterus  and  Fallopian  tubes.  The  free  surface  of  the  mucous 
membrane  is  lined  by  a  layer  of  epithelium,  generally  of  the 
columnar  variety ;  the  exceptions  are  the  mouth,  upper 
part  of  the  larynx,  lower  part  of  the  pharynx,  oesophagus, 
tympanum,  intercellular  passages  and  air  cells,  lower  part 
of  the  vagiua,  bladder  and  urinary  passages.  The  cells  se- 
crete a  fluid  called  mucus,  which  is  intended  to  lubricate 
the  surface,  and  protect  it  from  the  contact  of  air,  and  an}' 
irritating  substance  to  which  it  may  be  exposed. 

Mucus  is  a  transparent,  viscid,  tenacious,  semi-fluid 
substance,  insoluble  in  water,  but  may  be  readily  dis- 
solved by  any  alkali.  It  is  coagulated  by  weak  mineral 
acids,  acetic  acid,  and  strong  alcohol.  A  substance  resemb- 
ling mucus  may  be  obtained  from  any  inflammatory  exuda- 
tion, or  even  from  pus,  by  treating  it  with  liquor  potassa 
and  agitating  it.  Any  irritation  to  the  mucous  surface, 
from  wliatever  cause,  will  increase  the  secretion  of  mucus, 
as  for  example  the  use  of  snufF,  etc.  It  consists  of  about 
93  to  94  parts  fluid,  and  from  6  to  7  parts  solid  matter. 
The  organic  matter  is  termed  Mucine  or  Mucosine.  Mucus 
of  the  nose  consists  of ; — (Robin) 

Water 93. 3 

Mucine 5.4 

Fatty  and  Extractive  Matter. 3 

Salts '. 

icx).oo 

The  salts  consist  of  sodium  and  potassium  chloride  .6 
parts ;  sodium  and  potassium  phosphates,  sulphates,  and 
carbonates,  and  lime  phosphate  .4.  The  part  of  the  body 
from  which  the  mucus  is  obtained  may  be  determined  by  the 
form  of  epitheliun-  present  in  it,  the  result  of  desquamation, 
It  has  an  alkaline  reaction  except  in  the  vagina  where  it  is 
acid. 

Structure. — The  mucous    membrane,   like   the    serous 


being  largely  supplied  by   spinal  nerves,  while  the  rest  of 
the  intestines,  stomach,  and  oesophagus,  are  more  directly 


r 


MUCOUS  MEMBRANES.  !().-> 

and  synovial,  consists  essentially  of  three  parts  ;  the  epith- 

eliuvi — the  basement  meTnhrane — and  the  areolar  tiisue,  in 

which  the  vessels,  nerves  and  lymphatics  are  imbedded,  and 

which  connects  it  with  the  subjacent  parts.    The  latter  gives 

the   membrane    its    thickness,  and   is    made  up  of    white 

fibrous,    and   yellow   elastic   tissue,   vessels,   etc.      In   the 

raucous    membrane    of    the    erectile    tissues,    as    in    the 

organs  of    generation,   some   nucleated,  fusiform,    mu.scu- 

lar   fibre-cells   are   seen   imbedded    in   the   areolar  tissue. 

The  epithelium  not  only  covers  the  free  surface  of  the  mem-  gf» 

brane,  but  also  dips  down  to  line  the  follicles,  ducts,  etc.    It  ^ ' 

also  covers  the  surface  of  the  villi  and  valvular  conniventes. 

The  relative  amount  of  vessels,  nerves,  and  lymphatics,  de-  H 

pends  upon  the  activity  of  the  parts;  the  vessels  are  also  jii' 

more  tortuous  where  a  large  supply  of  mucus  is  requisite  «v ;. 

Some  parts  of  the  mucous  surface  are  not  so  sensitive  as 

others ;  for  example,  the  passage  of  food  is  not  felt  ir   the 

oesophagus,  stomach,  and  intestines  until  the  fiwcal  matter 

reaches  the  rectum,  when  a  sensation  is  felt  demanding  its  ' 

discharge.  This  depends  on  its  nervous  supply — the  rectum  >,  i 

i*  i 

under  the  influence  of  the  sympathetic  system.     Mucous  »> 

surfaces  are  not  disposed  to  form  adhesions  in  inflammation, 
owing  to  the  presence  of  the  epithelium  and  mucus.  These 
change  the  character  of  the  plastic  material,  and  cause  it  to 
degenerate  into  pus ;  but  if  the  epithelium  be  entirely  re- 
moved a  partial  organization  takes  place,  as  may  be  seen  in 
the  casts  of  the  alimentary  canal  in  dysentery,  when  not  of 
a  very  low  type. 

APPENDAGES   OF   THE  MUCOUS   MEMBRANE. 

In  most  parts  of  the  body  the  mucous  membrane  is  pro- 
vided with  papillte,  and  follicles,  or  glands.  In  the  aliuieTi- 
tary  canal,  the  mucous  membrane  is  thrown  into  folds  called 
valvulae  conniventes.  There  are  also  velvet-like  projections 
called  villi.     These  are  termed  appendages. 


I 


100 


^fE^fnRANo  i  ^.v  jcxpjns/oxs. 


Patill^'. — Of  tlioso  tlioro  arc  two  kinds,  f</n)iigt/  or  Vds- 
ntlar,  as  found  in  the  tongne,  etc.,  and  rough  or  /on??/,  as 
i'ound  in  the  intcgmnents  of  tlio  palnia  of  the  har.ds  and 
solos  of  the  feet.  Ir.  the  integument  they  are  tlie  organs  ol 
touch  or  iitdllc  orifans  ;  in  tli(>  t  )ngue,  tlie  organs  of  (he 
special  sense  o{' t(tstc,  and  also  of  touch;  the  former  will  be 
described  with  the  integument. 

'■'-  '"'•  A  ]iapilla  is  a  slight  ele- 

vation of  the  surface  of  the 
membrane  of  which  it  forms 
a  part,  consisting  of  tiie 
basement  membrane  cov- 
ered by  one  or  more  layers 
of  e[)itln'lium,  and  contain- 
ing within  a  reticula  of  cap- 
illaries, nerves  fcjrming 
lo()})s,  lymphatics,  and  in 
s  lO  instances  nonstriated 
muscular  fibre- cells,  the  lat- 

A.  tiUiiiionis  i>ai>illu  ol  the  luiiKl;  n.  edit ica    tor     CaUsiug     it     to    COUtract 
iiiviT  witli  colls  and  olnsti>'  filiros;    h,  tactile  ,  , 

lorimsde  ;  c,  nine  fibres  (Kolliker).  and  bcCOUie  ])r()minent  wllCll 

any  irritation  is  applied.  Some  of  the  pai>illa»  are  cleft,  as 
for  exam]ile,  those  in  the  back  part  of  tiie  dorsum  of  the 
toniiue  and  in  the  hands. 

The  papillae  of  the  tongue  may  be  divided  into  s'im])lc 
and  ccmiHUind.  The  sim|)le  pa})illa'  are  dispersed  over  the 
.surface  of  the  tongue  among  the  compound  forms.  The 
compound  are  the  cu'cumvallaie,  fanglform,  and  jillform, 
and  are  visible  to  the  naked  eye. 

The  circumvdllatc  pa])ilhv  are  of  a  large  size,  and  vary 
in  number  from  eight  to  ten.  They  are  situated  on  the 
dorsum  of  the  tongue,  near  its  base,  and  consist  of  a  row  on 
each  side,  which  runs  obliquely  backwards  and  inwards,  to 
terminate  in  one  large  papilla  situated  in  the  median  line, 
called  the  foramen  cceciim.  Ihe  two  lines  resemble  the 
letter  V  inverted.     Each  papilla  consists  of  a  circular  flat- 


MUCOUS  MEMBRANES. 


107 


toned  |>n>joction  of  tlie  mucous  membrnno,  from  j'^  to  ,'j  of 
an  inch  (I  to  2  mm.)  in  diameter,  surroundid  liy  a  narrow 
circular  fissure,  this  fissure  being  again  surrounded  by  a 
narrow  circuhir  elevation  of  tlio  mucous  membrane.  The 
whole  suiface  of  these  papilho  is  studded  with  numerous 
smaller  or  secondaiy  jtapillio,  and  investtid  with  epithelium, 
the  deep  layer  being  rounded,  the  superficial,  scaly. 

I'M-.  47. 


The  toiisiuo  with  its  piipillif  ami  iiervos,  (llcrscliluld). 

The  fuvglform  ])apilI;o  are  scattered  irregularly  among 
the  filiform  papilho  on  the  dorsum  of  the  tongue,  but  chiefly 
at  the  sides  and  a[)ex.  They  vary  from  o^  to  .j^  of  an  inch 
(I  to  .7  nun.)  in  diameter,  generally  narrower  at  the  base 
than  the  sunnnit,  and  studded  with  numercms  smaller  pa- 
[)ill;o,  like  the  }> receding  variety.  They  have  a  reddish 
color,  owing  to  the  thinness  of  the  epithelial  covering. 

The  filiform  impilUn  cover  the  anterior  two-thirds  of  the 
tongue.  They  are  conical  in  shape,  and  vary  in  thickness 
from  6*0  to  Vo  of  an  inch  (.5  to  .3.5  mm.)  and  are  about  -r\,  of 
an  inch  (2.5  mm.)  in  length.  They  are  pale  in  color,  owing 
to  the  density  of  the  epithelium,  and  are  also  covered  with 
7 


c 


J 

<t 

f  ■   , 

1 

I  •-  ' 

1 

1 .  J 

i 

♦'■■ 

v 

108 


MEMBRANOUS  EXr  I  \     / 


\\ 


■;i|-;  \ 


:  r  1 1 1  •  f  I  i 
i  1 1  i  1 1  u  I 


numerous  secoudary  papilhe,  sonic 
hairs  from  joVo  to  j^Vir  ot  an   iin  ' 
thickness  and  about  A  of  a  line    i 
papilhw,  the  mucous  membrane  oi    ' 
with  a  number  of  follicles  and  glan 
cial  organs  of  taste  called  ta8te-V)U'l 

Follicles. — These  are  found  in  u 
branes.     Those  of  the  tongue  an 
those  of  the  stomach,  gastric  folli 
tines,  simple  follicles,  or  Lieberkiili>i 
uterus,  uterine  follicles,  etc.     In 
tially  the  same.     They  consist  ol 
sions  of  the  mucous  membrane,  or 
of  a  glove,  arranged  perjiendicul  : 
which  thiy  open  by  minute  apei  i 
of  a  basement  membrane  lined  b> 
erally  columnar  on  the  sides  and 
covered  externally  by  the  vessels 
stances,  as  in  the  stomach  neui 
subdivide  into  from  two  to  foui-  i 
pouches,  and  are  sometimes  con\  > 
instances  they  are  arranged  like 
stem,  and  are  termed  racemose  as 
of  the  pharynx,  trachea,  etc. 

The  mucous  membrane  of  the  > 
honey-combed  appenrance,  consi-t 
pits  or  de}n'essions,  from  j^-^  to 
mmm.)  in  diameter,  separated 
In  the  bottom  of  these  depressions  are  seen  the  openings 
of  minute  tubes,  the  gastric  follicles.  These  are  divided 
into  two  varieties,  mucous  follicles,  or  those  that  secrete 
mucus,  and  gastric  or  'peptic  follicles,  or  those  that  secrete 
the  gastric  juice.  These  two  varieties  differ  only  in  the 
character  of  the  epithelium  which  lines  them.  The  mucous 
follicles  are  lined  by  columnar  ei)itlielium  on  the  sides  and 
rounded  in  the  bottom.      In  the  pei)tic  follicles,  the  deep 


■"^'o'' 


:il      I 


\l 

redu 
taini 
|)hat 
aroui 
circu 

Jto 
The> 


:l  II II 

1        |m: 


r^l  11  iiM  I 


I       I  !  •'  !■  I 


III'  I 

-   / 


■  I      III         .  I , ,     I       '.111     '  1 1 
'  i  I '  t     I  I  I  ■  ■   \  I   I  ■  \     n 

■  -    ,11     I     '    ■  1 1    I    I       1 1        '  1 1 1 1 1 


.yi,  .,'1 


I'l    I  ! 
!  ;  1  1 1   I  ( 


I 


M  I      I 


I. 


I  :  I  I       Ml         I  ' :  I  I  I  ' 

' I  i  '  ■     M  l!  'I  I     I  U 

;  I    '  <'■■ 


I'll  I 


;  I  1 1 '  I       I  -        I 


,;/    ^jV 


sh.l 
Ih'  I  C.I   1.1  I     \  ,i  1  \  '■  .,    1(  '^l~^    1.1     I  In:    I  I'Cl.lllll,   etc. 

ValvulyE  Conniventes. — The  valvulse  conniventes  arc 
reduplications  or  foldings  of  the  mucous  membrane,  con- 
taining between  them  vessels,  nerves,  and  lacteals  or  lym- 
phatics imbedded  in  areolar  tissue.  They  pass  transversely 
around  the  cylinder  of  the  intestine  for  about  |  or  f  of  its 
circumference,  being  about  two  inches  in  length,  and  from 
J  to  f  of  an  inch  (8  to  16  mm.)  in  depth  at  the  centre. 
They  begin  at  the  hepatic  flexure  of  the  duodenum,  and  in- 


110 

entr.'iii 
diinii 

wluM' 

and  < 

nivrii 

inci' 

tlie  i! 
are  i ' 
oftli. 

laru- 
the  1 
hill  I 
t«  >  ■■- 1 
tow 

\    , 
of   i 


A  section  of  mucous  membrane,  sliowing  Peycr's 


II'.:    1 1  \     \  .  I    I  .  1 1 ;  1 1     j  >  I  '  1 1 1 1 M  :_:_■  - 

rttioiis,  or  (.'Vcr.siun.s  (;l'tlic 
mucous  membrane,  aud 
give  to  its  surface  a  vel- 
vety appearance  (Fig.  49). 
They  are  conical  or  fili- 
form in  shape,  and  vary 


x\  Dccuioii  oi  mucous  memurane,  showing  I'evcrs  •      i  l\    r  ,     .  n 

glands,  surrounded  by  the  openings  of  Lieberklihns  ^  lengull  irom  ,^g  tO  ^'fj  Ot 
follicles  and  covered  with  villi.  •       i      /  -i   i        i  \  ■» 

an  men,  (1  to  A  mm.)  and 
from  Ti^o  of  an  inch  in  thickne.ss  at  the  base,  to  y|„  of 
an  inch  (.4  to  .IG  nun.)   near  the  summit. 


lie   villi  are 


UllO 

.syst 

D 

ted 
The 

(2.5 
tissi 
byr 
ous 
In  ! 


:/  /:/<.!. \/:S. 


II 


inn; 


111   t.li(!  (Inodcinnn  and  jojuiiuii), 
'  iiiiuity  ill  a  sciuarc  line  ;  but  they 
1''  ileum.      Tlie  total  number  for  the 
|i\vardH  often  millions. 

ich  villus  consists  of  a  basement  mem- 
li  a  layer  of  columnar  e})ithfcliuni,  exter- 


in  its  interior  a 
lies,  nerves,  and 
of  the  lacteal, 
lid  iat  ghjbules 
hrld  togethei' 
Iso  contains 
I  ii     liliii'-cclls. 
I    I  ;i  1  III     pii  .|,l||- 
l  1 ' '  ;  1 1 1 1  •  I    1 1    ( ■  n  1 1  T  >  I  1 1 1 
(i.'i  |it  cr  ell  ;i  I'M  i|  |i|  inn 

'!    !lrv\<'-,    liJi-,    \\i  .(     l,c(   li 
I  III"  '11,1 1  ;i1  111,  1, Ml   I  lii\ 

■    •'■■>'-  t  ,        Am  i|  '  I  i  lr_'     I  .  ' 


(KiK.  50.) 


! 


<: 

««^*;. 


i.nie  comineiict  im  111 
.svsteni. 


>[  III'  ,1 1' 


l;ir\   iiutuiirk  ;  .-,  siU'Xilh  iiiii-,i  uUir 
liliru  ;  (/,  liicteul. 


Duodenal  OR  "Brunxer's"  Glands. — These  are  lirsd- 
ted  to  the  duodenum  and  commencement  of  the  jejunum. 
They  are  small,  ovoid,  lobulated  bodies,  about  ^V  of  an  inch, 
(2.5  mm.)  in  diameter,  imbedded  in  the  submucous  areolar 
tissue,  and  open  upon  the  surface  of  the  mucous  membrane 
by  minute  excretory  ducts.  These  glands  are  most  numer- 
ous near  the  pylorus,  and  diminish  from  above  downwards. 
In  structure,  function,  and  in  the  character  of  their  secre- 
fion,  they  rosomblc  the  lunercas. 


■  & 


WW  < 


i'>iin.l      w  Inn    li     I.,., In-      hnin    niir  luiiilli  n|    t\     linr    In  ii    liii.' 
I    '   <'>      '   n\m       Ml   i|  iiinicd  I  ,  run  ilihilu,   (i(    cImu'iI    xciirlci   liiiv 
Mil'     Hii     M|i|>!lli'H(     ('\(lr(.>iv    ilncl.nilil     lllll<l»'    up  nl     mlolinlil 

<  iM'Oi(>.  III!'  iucmIu'i  oI'  wlin'li  coiiliviii  «,  wliiliMli  hitii'I  ion  cum 
MiHlinj'  ,»|'  niit'lrniotl  coIIm  m  lvin|ili  t'oi'iuiHclcM,  niii'loi  mikI 
j>rau»il»ir  immHim  (V\\y  HM  Mih'Ii  lollirlo  \h  Hmronndod  Ity  n 
1\  iMplwHii'  vi'*'((>|,  Mini  n,  imImuIo  vm'umiImi'  ih>I  wuiK.  (Vuin 
(ho  1mII(M',  I'Mpillni'V  vcmmcIm  |»mmm  iitlo  ll»i«  iiili>riiti  innl  n>(iirM 
in  loi>|u,  In  {\\o  l.)\r»>r  p;n  I  ul  Iho  Mninll  in(t«M(in*>M  IIh>v  ni> 
IVUX'"'^^I''*''*'I  (oij;i>||»(M'  in  rinMilin  of  ovii.l  pulclioM.  (Voni  Iwrnly 
<<»  iMily  in  nnniUcr.  cmIIimI  /V'v<'I''n  fuitrhrs  or  iilmhlitht' 
iiifuii  ihtt.v  'ri\(«>*('  MVi'  inolo  nnnxMonM  in  lli<>  Iowit  piiil.  oI' 
dx'  ^.^u;^ll  ml«".(  inc*.  i\n>l  miv  silnnd'tl  «»n  (Ii.mI  pinl  oj'  Hip 
<i>lu>    lu.'.i    ,li.|;in(     I'liMu    (111'    Ml  l;i.'lini.ii(   ol    lln'  m,'  .>iil  .'r\ 

^^•''iN    I'  \  I    IM.I   .      II  .      ;||  .,<    I.'MU.I     HI     (  lie     I    II     '.      in(  I     .1  111.     ,         I'll.    II 


n    '  \  \   1  I 


I    ■  \  .'Ml.         I    I  '.  (      \  I    I    .  I  I  {   '  I  ' 

I       I  I  I  '     '  1  I      I   I  I  .       I  I  I  U'         M         I I  I  <l   .  I  I  I  , 

M  I  ■  \       .'(III        Ml     \       ;  I  I  .  '  I  I  '  I  ' 

I  .    '  .     I  i  \      h    n  I      '  1 1     I  i  I .  ■    I  .  I  .    .   . 

■        .      .      I        '     I   I        ,     :         II  1  ,  i      I  I  I  ,      '    .  •     ,  1  ,     \    , 


I'N 


III 


'    ''■'   i  ■   '•  i  I  i>  '  .  1    l'\    1  ill'  ,;  1  Hi  1 11,1 1  1,  'II   ,i(    [MM  .(Ml. HI'.  n\,i(  I  ri    1 1  om 
(iu^  M>\>.1       In  |>h(li;sis  thi'V  \\\:\\    l>.>ciMUt'  the  si>m(  of  HiImm' 
o\ilnr  liop^wit.  wluoh  soJhMis  .-uhl    nK'»M;it<>s,  rcsnllinj^'  in  a 
(umMosvMno  t\uni  of  vlianhuvi. 


INTIaU-MKNT. 

Tho  intOi>umon(  tvson\blos  tlio  oiIum-  luonUuanou.s  (Expan- 
sions ij>  it.s  ovnov.-»l  stnu'tinv.  anil  u»iol»(  Ih>  iH»nsi(lor(Ml  jim 
rtn  ovortcd  tnnoi^u^^  nion\br;\no.  It  I'ovors  ;\\u\  prottH't.s  (h(> 
Iwly   ;>;':, M\->  .^r  nK>(ion.  aiul  tnoro-os  i;r;uhi;\Ily  into   (ho   n»u- 


(  I  ; 


I  I    CMll  •.I'll    mI    I  lllin    |>'M  I    ',,    \\\i-    ifnlhrl  t  It  ni  ,   hin'ritl'lll     III  r  HI. 
hlKllf,    (Mill    Mk'    V"  TII'I  1,   IK'I  V<"l,    lyMl|tllM,I.M'  ;,  cl.r  ,  I  Itl  1  Hi  l<  !<' I    ifl 

(i.it'nliii   liMMiip.  cmIIimI  l.lir  fill  ill  III  oi   fine  "lull  (nil, in  vciuj 
I'll'irilKMIfM,  flicro  ('(ill  IIk    r.i, 

vi\  t'liiilmnin)       TliiM  in 

tiol.  |H<iin('Mlt>(l    l»y    vcM  ^ 

hpIm,    ih     inticli     lli'n'l<<"i' 

Minii  ill  «.ny  oilier  inciin- 

liiniin,     mill     nillHlHl.M    nj" 


MIWiMlll      Iliyi'lH     (il     ('(IN 

tliiiri'ii    \y\   i'i'mx-mI'  finli 


,1 


('      I 


Till-  liiMl,  Invr.    '    ;Vv^0//''^iJ''■ 


/ 


mIiiiico 

or  I  liu'ii'  u  Incli  (lie  Mi'\|, 

Mil'  l<;i  wini'iit   iiii'liilil  line     ' 

;  I  I  ,       (  .  1 1  II  I M 1 1 ;  I  I     III     I  M 1 1  I  p  I  / 

.  .  I      I  . , .  I   I  r  , .  : .    ,  I  .     I        I  I  I .  .  I 

(In       I  M  I  I  '    '  '  II  I    I  \   '    I  I  '    I 

I  II  I  III  '     M  I  I  I    <  U  M     I  I  I  'I       I  I  I    I  I  I  I 

I     I    ',    .     I  I  I  I    I    '   I  I  I  I  I  '   I   I  M 

i    In      -.  .■111!:  I I,  I 


:•  :■;//;! 


an  iiH'li  .  S  III  I II  III  )  III  'lijiiieli  T,  iJie  Mi|'i'r(ieifi,l,  ,,,',,,  H  Li  iniiini  ; 
Tlin  e|iii|eiiniM  c.uversi  l,li(^  wlioki  Hill  race,  iumI  Ih  not  very  nrii- 
fonn  in  thiclvnes;;,  liein;^'  v(My  Miin  in  tli(!  j^rr/m  an<l  axilla, 
nnd  (hick  in  tlie  pjilins  of  tlin  IuukIh  and  Holes  of"  tho  feet. 
Tlio  thicknesH  of  the  cutif'ie,  in  hoiiu!  paits  of"  tlio  fcof,  ^ives 
rise  to  corns.  Tlu!  (hivelopnient  of"  the  ccijls  tak(!S  ]:)lace  at 
tho  ItaHenient  tneinhiaiie,  and  as  tlioy  a|)f»r(>a(!li  fclie  surface 
they  become  chani^ed  in  shape,  and  nitiniately  fall  off  by  a 
jjjfadual  proeess  of  desipiainal-ion.  In  some  of  f/he  oxanthc;- 
uial.'v,  as  scarlet  I'ever,  measles,  etc.,  a  {'niiiple(,e  fleKipiainatioii 


■it, 


<i|  I  111'  I'lilicli'  l;i,k.'s  pliLco  diiiiiijj,'  recovery.  in  I  lie  serpent 
(.iil)e  an  ('xuviaLiuu  occurs  annually.  'I'lu-  nuter  layers  of 
cell.s,  when  exposed  to  the  action  of  acetic  acid,  swell  out 
and  become  rounded,  .showing  tl'.eir  original  shape.  A  solu- 
tion of  caustic  potash  also  makes  them  rounded,  and  com- 
pletely destroys  the  deep  or  mucous  layer,  as  it  is  called. 
The  epidermis  is  pierced  by  the  hair  follicles,  sudoriferous 
ducts  and  sebaceou:^  follicles ;  these  openings  are  called 
pores.  In  chemical  composition  it  resemV)les  hair,  horn,  nails, 
etc.  In  parts  subjected  to  irritation,  as  the  integument  of  the 
laborer's  hand,  and  beneath  corns,  the  vascular  supply  of 
the  cutis  is  increased,  in  order  to  supply  the  cells  more 
abundantly. 

('OLOU. — Tlio  color  of  the  different  races  is  due  to  the 
develDpini'nt  oC  minute  p;irtieles  of  piL^Miient  ni.itter,  tVoni 
I     '  , , , ,   t  w    ,     ', ,      ( 1  r  ;  1 1 1  i  1 1 1  •  1 1  1 1 1  ■  1 1 ;  1 1 1 M '  I  < '  r     i'  .")  t  ^  i  I  •_!.">  n  m  1 1 1 1 1    .in 

ill''  IllIrM'  i|-  I  r  -.  MM''  ■  i|  ill  I'i'l  i-^  .  it'  I  '  h'  111'  I.-. /I  I  ,  l;i  \i'r.  'I'lleSi' 
(•el  |>  ai'e  I  liefi'j,  ,lr  e;i  I  li'(  ;  j  if/iiir  n  /  e.  // ,  ;|  |  p  |  ;iri  ■  v,i  ■  |-\-  ll  1 1  1 1 1  e)'- 
Mll-.    in    llie      I'll  ii  |M[i|;U|    r;ir''  \'\\r     I 'i  i]  i  ifi  1 , '4'     lli:|lt''l'    '_''i;i' I  i  1;  I  II  \' 

I  I  I  111  I  III  -Im    -     I    .w  :i  I'l  U     ill.         I  I  I  l.ir.  ■    (  i|      (  lie    ,  ■  ,  ';i  |.   I  111  I  -         Tlii'    ■  li' 


n 

ai 

col 

eel 

cal 

it 

con 


re,!L^ 

(.<■ 


;iM  ()l;i,  "I  tile  nipple,  and  other  jtart.s 
of  the  body  in  pregnant  women,  ntievi, 
freckles,  etc.  They  may  assume  dif- 
ferent shapes  ;  some  are  rounded,  as 
those  of  the  epidermis ;  others  poly- 
Pifem.ent  cells.  ^^^^1,  as  the  epithelium  lining  the 

inner  surface  of  the  choroid  coat  of  the  eye ;  while  those 
imbedded  in  the  substance  of  the  choroid  ^^'-esent  a  remark- 
ably stellate  appearance  (Fig.  52).  Those  which  line  the 
inner  surface  of  the  choroid  contain  a  large  quantity  of  pig- 


Micnt  nrijinulcs.  i'i^niictit  ;_M'aiml(>s,  wlicn  viewed  separatelx-, 
are  traii.sj)arcnt ;  but  when  viewed  collectively  have  a  dark 
color,  and  are  seen  to  move  about  when  set  free  from  the 
cell,  sometiincs  even  when  contained  in  it.  In  their  chemi- 
cal nature  they  resemble  the  cuttle-fish  ink,  which  derives 
its  color  from  the  pifcment  cells  liniuor  the  ink-bajr.  Pi<rment 
contains  from  forty  to  sixty  per  cent,  of  carbon.  In  some 
persons  there  is  an  entire  absence  of  pigment,  as  in  the 
albino ;  the  hair  and  skin  are  unusually  white,  and  the  iris 
has  a  pinkish  hue. 

Basement  Membrane.— The  basement  membrane  covers 
the  cutis  or  corium,  supports  the  cells  of  the  epidermis,  and 
regulates  osmosis.     It  is  distinctly  seen  in  the  integument  - 

of  the  fd'f  ^  is  not  |>eree[>ti!)le  in  t'  It. 

</<)im;M,  oil  i  'I'l'is  \'ki;a. — The  CMrinin  eoiiM>ls  of  v>'sse|s. 
liiT\-('-..  l\-iii]i|i;i  I  irs,  ;i  w  1  iu|  i -,  h  i ;( I  >  ■■  1  iiMi-riil;ir  I  i  I  u  v- ,  ■,  1 1 -,  ;n|i| 
:<<>\t\i'  t;il,  Hill  iciMr,  1  ill  ;ii  i!)!,if  tl^-,llt■  |'i_;-.  ;,  |  .  Tlif  iih'-lii'-, 
mI  till'  arewlnr  ti^>iir  mv  \rr\  mmmII  tnwiuiU  llii-  ^llliae(^  Inn 
••u'''    laij-'T    lowa.nl-.    tli.'    -^iil  .jaei'Dl    tl    -lev       In    part-,    wlict,' 

■•t  1  rtlL'l  M     i  ■,    ici  |nii  .•,!,    1  ''1.      W  lill  (■    ri!)i'.a|-     ll  -ai.      j  ■  i  ■   ,  1  ■  i , ,  i  l  l  i ;  i  ,  i  ■ 


*  li« 


throug  iie    wliijle  extent  of  the  cutis,   .s(;nu?  of  them 

surround  the  papilUu  and  hair-bulbs,  and  give  rise  to  that  5 

peculiar  roughness  of  the  surface  called  cutiti  anserina,  as  is 

seen  in  the  cold  stage  of  intermittent  fever.     They  are  very 

abundant  in  the  cutis  of  the  scrotum  (the  dartos).     Fat  is 

found  in  the  meshes  of  the  deeper  parts  of  the  corium,  form-  ' 

ing  a  soft  bed  on  which  the  skin  rests,  giving  rotundity  and 

symmetry  to  the  body,  and  from  being  a  bad  conductor,  it 

prevents  the  too  rapid  escape  of  caloric.     The  integument  i 

may  be  tanned  by  any  substance  which  will  precii)itate  the 


n»ll;i'f 'II,  as  nai,  i(;ii  u,  hep  lock  liaik,  etc.,  tln'  tannic  aci<l  (»t" 
wliich  unites  with  tlic  cullai^a-n. 

AITKNDA(iKS   OF   THE   INTECJUMENT. 

These  arc  tlio  papUlce,  nails,  hair,  sebaceous  and  sudorif- 
erous glands  and  ducts. 

Papill.^':. — The  external  surface  of  the  coriun  is  raised 
into  papillary  eminences,  carrying  with  them  the  basement 
membrane.  They  arc  irregular  in  size  and  frequency,  except 
in  the  palms  of  the  hands,  soles  of  the  feet,  and  surrounding 
the  nipple.  The  average  size  of  the  papillse  is  too  of  an 
inch  in  length,  and  i,),,,  of  an  inch  in  diameter  at  the  base. 
The  interior  of  the  papilhe  consists  of  capillaries,  nerves, 
and  lynijihat  ■;.  in  areolar  tissue.  Tlie  nerves,  as  in  all  liner 
tli\isiiiiis,  ail        stiliitc  of  tlic  wliitc  snlista.nci'  oC  Scliwanii. 

ail'l     ;  lirivt'  n    .     il  llti.'ll  ll      <.r    .  |.    li'Mh     I  r;|  (  j/  ,||  Tll''\      ;  i  j  1 1  "  :\  1      {•  ■ 

I  ii  111  n;,i  I ''   III   iii;i  n  \   >  <\   I  lir  luon'  -m  -i  I  i  \  •'  |  t;i  pi  11:'  ■,  a  .  (  li'  i  .!•  i  il 

ill''    Il   Mill    ;ill'  I    lip-.,    Ill    <  i\  ;i|       li;i  pri  I     I  m  m||i   s    c;i  I|im|     l;ii't  ilr    en  I' 
pll    I'll        I  |''i    i-      Id      A  Tiir-.-     I.d^li.-     ;nv     <;.'l|r|  ;i  i  I  \'     I  .  • -'Ml  .  1.  ■.  | 

.1       !  1  !  t  I ,  ■     III,!-     ,     .    .  .  r    r    '  1 1 1 1 1   I   I  I  \  .  ■     I  I       .  I    ■        I  i  1  I     ■  1 1  M  '  1 1  ■  >  I      I    \       ■  I :  I     t  1 1  • 


tl 
I. 
f( 

eti 


i 


liaui|->,  and  sdlcs  ut'  the  h'et,  they  are  numerous,  anil  attain 
a  largo  size,  and  are  so  arranged  as  to  form  ridges  on  the 
surface,  which  are  generally  more  or  less  curved  and  separ- 
ated by  grooves.  This  appearance  can  be  seen  with  the 
naked  eye.  Each  ridge  is  produced  by  a  single  or  double 
row  of  papilla3  projecting  from  the  surface  of  the  cutis,  and 
covered  with  the  epidermis.  The  papillne  in  each  row  are 
generally  arranged  in  pairs  side  by  side,  each  pair  being 
separated  from  the  next  adjacent  pair  by  transverse  grooves 
which  cross  the  ritlges  at  right  angles.    In  the  centre  of  each 


traiisvorse  jj^i-oove  iiiay  Im;  seen  tlu'  oi-ificti  oj"  a  sweat  duct. 
In  a  s(iuare  incli  of  the  palm  may  be  seen  twenty  riilces,  or 
forty  rows  of  papilhe,  and  ratlier  more  than  sixty  pair  in 
each  row. 

The  office  of  the  papillfie  is  sensation  or  touch,  and  to 
increase  the  surface  for  cell  development.  They  are  covered 
and  protected  by  the  epidermis,  which  also  fill>i  in  the  sjjaces 
between  them. 

Nails. — The  nail  is  an  extension  of  the  epidermis,  very 
much  hardened,  in  order  to  form  a  protective  covering  for 
tho  dorsal  surface  of  the  terminal  jthalanges  of  the  hands 
and  feet.  Each  nail  consists  of  a  root,  body,  and  extremity. 
The  cutis  i.s  folded  upon  itself  so  as  to  form  a  groove,  in 
which   tile       'ut  and  ]u}i\y  of  t1i(>  nail  are  iiiilie<lde<l  ;   this  is 

'•ailed     the     lintri  \-      liee;illsr    if      is    tile     -.c.-it    i  if    -Tm  W  t  1 1 ,         N.;if 

I  111  1-1  11  il  1  it  ill.'  Ii;i,i  I  lil.l  \  I  ■.!■  -1  <  II  ;l  I'hi  i  '  I  '  I  ;  il  lr;i  1  W  I  i  II  ■  -  ]  m  .1  , 
e.llie.l  (lie  hinll'il.  I'Im'  -,1  n  let  i  i  ri  •  m|  ih,'  ||:i||  |-  (I,,.  -.;niie  as 
(  lie    e|  il.il 'nil  i-  ;     It    ei  III-  i     I  .  nf   ,i-\  rra  II;  I  ■,  ,  i  f  er  ||  ,   i  1 1  i  •    )i|,'i|| 

-III  isl  ;ilier       I  hr     i  j.-r  |  i     les'      I  ..sllj'     I  i  illlli  ji   '  f     '  Iw      1  1 1  >  .,.  I      ;  .\  ;i  |     i  ,r 

'■I"!..    ■'.■■■  I        .Ml'  i      I   SI         II  se,  s'         lis  lis  I  e    I,,    ,  I      s  IS  i       \  .    ]   \        II  :     s-l 


'*u-. 


I  I  I  y ,  I  I  I  ^ 


el. 


in     I M 


the  naked  eye,  for  tho  purpose  of  increasiug  the  cell-fdiniiug 
surface.  The  vascular  and  nervous  supply  is  vary  abundant 
in  the  matrix.  In  long  illness,  particularly  of  the  mucous 
surfaces,  the  nails  are  marked  by  a  transverse  groove,  the 
size  of  which  is  an  index  of  the  length  and  severity  of  the 
disease.  It  is  caused  by  the  abridgment  of  the  nutritive 
process  for  the  time  being.  This  peculiarity  is  taken  ad- 
vantage of  by  fortune-tellers,  gipsies,  etc.,  who,  by  examin- 
ing the  nail,  are  able  to  tell  the  person  when  he  was  sick, 
and  the  dui-ation  of  tho  illness,  from  the  size  of  the  "Toove 


I- 


118 


MEMBRANOUS  EXPANSIONS. 


Figr.  53. 


and  its  distance  from  the  root.  The  nail  increases  in  length 
by  the  development  of  cells  at  the  root,  and  on  the  under 
surface  of  the  body,  which  push  it  onwards  in  its  growth. 
The  finger  nails  grow  at  the  rate  of  about  \  of  a  line  per 
week,  and  the  toe  nails  about  -f,  of  a  line  per  month. 

Hair. — Hairs  are  found  on  all 
,  parts  of  the  surface  of  the  body, 
except  the  palms  of  the  hands 
and  soles  of  the  feet,  and  vary 
in  length,  shape,  and  thickness. 
They  are  implanted  in  a  saccular 
cavity  called  the  hair  follicle,  wh'ch 
is  formed  by  an  involution  or  dip- 
ping of  the  basement  membrane 
into  the  corium,  carrying  with  it 
the  epidermic  cells,  the  superficial 
layers  of  which  become  rounded. 
This  follicle  is  larger  at  the  bottom 
■jhan  at  the  top,  to  correspond  with 
the  bulbous  enlargement  of  the  hair, 
and  presents  in  the  bottom  a  highly 
vascular  papilla  covered  with  cells, 
from  which  the  hair  grows.    A  hair 

Hair  in  its  follicle,  magnified  .50.  .  '^ 

a,  stem  cut  .short ;  b,  root ;  e,  bulb  ;  COnSlsts  of  a  VOot Or  that  part  im- 

d,  hair  cuticle ;  e.  internal,  and  f,  ex-         ,,,.  />iti  ?/• 

ternal  root-sheath  ;  a,  h,  dermic  coat  bedded  m  the  follicle  ;    a  Sliaft tllO 

of  follicle  ;  i,  paitilla  ;  k,  k,  ducts  of  _  ■^ 

sebaceous  ijlands  ;  1,  corium ;  m,  mu- part  whlch  prOiects  frOm  the  SUr- 
cous  layer  of  epidermis ;  n,  upper  r  i.       j 

flattened  layers  of  epidermis  ;  o,  up-  face  ;  and  the  extremitV,  which  is 
l)er   hmit   of    internal    root-sheath.  '  ^' 

(lioiiiker).  sometimes  split.     The  root  is  the 

thickest  pavf,  and  presents  a  bulbous  enlargement.  The 
diameter  of  the  shaft  varies  from  ^U  to  -rsVo  of  an  inch  (100 
to  16.6  mmm.),  and  is  divided  into  two  parts — the  cortical 
and  Tnedidlavt/  portion ;  the  former  predominates  in  the 
human  subject.  In  structure  it  resembles  the  epidermis. 
On  section  it  is  seen  to  consli-t  of  cells  and  cement  substance. 
In  the  medullary  portion  they  are  rouuded  ;  but  toward  the 
circumference  of  the  cortical  portion,  they  first  becomn  oval, 


thei 

ed, 

an  i 

ger 

to  t 

to  t 

ext( 

line 

im 

mac 

caus 

man 


INTEGUMENT. 


119 


A  Kcctinii  (if  hair 


then  elongated  or  fusiform,  and  finally  flattened  and  harden- 
ed, and  the  latter  are  so  arranged  as  to  present 
an  imbricated  appearance  (Fig.  54).  If  the  fin- 
ger be  passed  along  the  hair  from  the  extremity 
to  the  root,  a  distinct  roughness  is  felt,  owing 
to  this  peculiar  arrangement  of  the  cells.  The 
external  surface  presents  fine,  sinuous  cross 
lines,  and  a  jafjcfed  boundL,ry,  caused  by  these   nvignificdatidshow- 

.         .        ''       ^    .  .  .  .  iniJr  tlie  imbricated 

imbrications.  If  a  longitudinal  section  be  appearance. 
made,  the  cortical  substance  presents  a  fibrous  appearance, 
caused  by  tlie  arrangement  of  the  elongated  cells  in  a  linear 
manner.  A  few  pigment  cells  may  be  seen  scattered  irre- 
gularly among  the  fibres  of  the  cortex,  but  they  are  more 
abundant  in  the  medulla.  The  color  of  the  hair  depends  on 
their  presence.  The  coloring  matter  consists  oi  melamue, 
and  is  readily  bleached  by  chlorine.  It  is  stated  that  the 
hair  has  grown  white  iu  a  single  night  from  the  influence  of 
some  depressing  passion,  as  fear,  etc.  It  must,  however,  be 
a  very  rare  occurrence,  and  can  only  be  explained  upon  the 
supposition  that  some  peculiar  fluid  is  secreted  at  the  papu- 
la, which  percolates  through  the  hair  and  destroy  the 
coloring. 

The  hair  is  increased  in  length  by  the  development  of 
cells  on  the  papilla  at  the  bottom  of  the  ^olUcle,  which  push 
it  upwards.  The  cells  which  are  developed  in  the  papilla 
are  originally  rounded,  and  those  which  grow  on  the  summit 
continue  so  throughout  the  medulla  to  the  extremity  of  the 
hair :  while  those  which  grow  fiom  the  sides  soon  become 
flattened  and  imbricated  as  they  pass  upwards  on  the  exte- 
rior of  the  hair.  In  some  animals  the  papillae  are  large,  and 
prolonged  upwards  in  the  central  part  of  the  hair  above  the 
surface  of  the  body,  and  hence  they  bleed  when  cut  or  ex- 
tracted. In  the  disease  of  the  hair  called  'plica  Polo7i{ca, 
the  papilla}  are  said  to  be  elongated,  and  bleed  when  cut 
close  to  the  skin.  The  hair  in  these  cases  grows  very  fast, 
and  becomes  matted  together  by  a  glutinous  secretion.  Some 


;.  !■■( 

•I«(:J 

liii  ■" 

■  -* 

li;;. 

1 

t 

11*    • 

3 

lie, 

11^ . 

1 

' 

i 

il-. 

p 

it 

120 


MEMBRANEOUS  EXPANSIONS. 


of  the  sebaceous  glands  open  into  the  hair  follicle,  and  pour 
out  an  oily  secretion  which  keeps  the  hair  smooth  and 
glossy. 

Development  of  the  Hair  Follicle. — At  about  the 
sixth  week  of  ftetal  life,  there  is  first  seen  a  slight  depres- 
sion or  inversion  of  the  basement  membrane  lined  by  the 
epidermis,  forming  the  rudimentary  follicle.  It  then  be- 
comes deeper,  narrower,  and  fiask-shaped,  containing  cells  ; 
those  in  the  centre,  fusiform  in  shape,  are  arranged  in  a 
line,  and  form  the  rudimentary  hair.  At  this  time  also, 
the  papilla  springs  from  the  bottom  of  the  follicle.  The 
first  brood  of  hairs  are  temporary,  like  the  deciduous  teeth. 
After  birth  the  follicles  deepen,  and  a  new  papilla  io  formed 
at  the  bottom  of  each,  from  which  the  permanent  hair  is 
developed,  the  old  hairs  being  cast  off.  When  a  hair  is 
plucked  out,  the  follicle  tills  with  blood,  which  after  a  little 
disappears,  and  '**the  papilla  is  not  destroyed,  a  new  hair 
will  spring  up  .uything  that  interferes  with  the  vascular 
supply  at  the  base  of  the  hair,  will  affect  its  growth  and 
cause  it  to  fall  out.  The  growth  of  the  hair  may  be  pro- 
moted by  the  application  of  certain  stimuli,  as  tincture  of 
cantharides,  bay-rum,  etc. ;  these  form  the  bases  of  hair 
restoratives. 

Sebaceous  Glands.  —  These  glands  are  found  in  most 
parts  of  the  integument,  except  the  palms  of  the  hands  and 
solos  of  the  feet.  They  are  very  abundant  on  the  scalp, 
face,  axilla,  groin,  etc.,  and  open  either  upon  the  general 
surface,  as  on  the  face  ;  or  into  the  hair  follicles,  as  on  the 
scalp  (Fig.  51).  Each  gland  consists  of  an  involution  of 
the  basement  membrane,  lined  by  the  rounded  or  mucous 
layer  of  epithelium.  Sebaceous  matter  is  secreted  from  the 
capillaries  beneath  the  basement  membrane  by  these  cells, 
which  at  maturity  break  down,  and  throw  out  their  secre- 
tion either  on  the  surface  of  the  body,  or  into  the  hair 
follicles.  In  some  cases  the  gland  is  lobulated  or  sacculated 
in  order  to  increase  the  secreting   surface.     In  the  scalp 


INTEGUMENT. 


121 


there  are  two  of  these  glands  to  each  follicle,  into  which 
they  pour  their  secretion,  for  the  purpose  of  lubricating  the 
hair.  The  excretory  ducts  are  generally  short  and  straight, 
and  in  some  parts  of  the  body,  as  the  face,  they  become  the 
habitat  of  a  parasitic  animal  the  i^teatozoon  Folliculortim, 
These  are  more  common  about  the  time  of  puberty,  and  in 
those  possessing  a  torpid  skin.  The  sebaceous  matter 
which  covers  the  foetus  is  called  the  vernix  caseosa. 

The  development  of  the  sebaceous  gland  is  similar  to 
that  of  the  hair-follicle.  At  about  the  sixth  month  there 
is  seen  a  knob-like  depression  of  the  basement  membrane 
of  cither  the  general  surface  or  the  hair  follicle,  as  the  case 
may  be.  This  soon  becomes  deeper  and  narrower  at  the 
mouth,  until  it  assumes  a  flask-shaped  appearance,  and  is 
lined  by  the  rounded  layer  of  epithelium. 

Ceruminous  and  Odoriferous  Glands  are  varieties 
of  the  sebaceous.  The  ceruminous  secrete  a  waxy  material 
which  entangles  particles  of  dust,  insects,  etc.,  and  prevents 
their  access  to  the  delicate  membrane  of  the  tympanum. 

Sudoriferous  Glands. — These  are  situated  in  the  deep 
part  of  the  corium  and  subcutaneous  areolar  tissue,  being 
surrounded  by  adipose,  and  open  by  a  duct  upon  the  sur- 
face of  the  epidermis,  (Fig.  51).  Each  gland  is  formed  by 
a  simple  involution  of  the  basement  membrane,  carrying 
with  it  the  deep  layer  of  cells,  and  terminating  in  a  convo- 
luted tube  beneath  the  corium.  Sometimes  the  tube  is 
branched,  the  branches  being  rolled  up  in  one  clump,  and 
held  together  by  areolar  tissue.  The  duct,  as  it  passes  to 
the  surface,  takes  a  tortuous  course  through  the  corium, 
upon  the  surface  of  which  it  loses  the  basement  membrane 
and  is  continued  on  through  the  epidermis  in  a  spiral 
course,  the  calibre  being  larger,  and  the  walls  of  the  duct 
being  wholly  formed  by  the  layers  of  cells.  It  opens  on 
the  surface  obliquely,  by  a  valve-like  aperture,  formed  by 
the  scaly  epithelium.  The  openings  are  called  pores,  and 
as  many  as  2,800  on  an  average,  exist  on  each  square  inch 


111  1 


( 

<l 

.4 

1 

if 


fiWjE 


122  MEMBRANEOUS  EXPANSIONS. 

of  surface.  The  number  of  square  inches  of  surface  in  an 
ordinary  sized  man  is  about  2,500,  therefore  the  number  of 
pores  will  be  about  7,000,000.  Each  duct  is  about  one- 
fourth  of  an  inch  in  length  when  unravelled,  and  the  total 
length  of  tubing  about  twenty-eight  miles.  This  is  a  very 
important  and  extensive  excretory  surface. 

Function  of  the  Skin, — It  serves  as  a  protective  cov- 
ering for  the  body,  and  possesses,  toughness,  flexibility  and 
elasticity — due  chiefly  to  the  presence  of  areolar  tissue  in 
the  corium.  It  possesses  both  the  function  of  absorption 
and  secretion.  Absorption  is  carried  on  through  the  lym- 
phatics and  capillaries  of  the  coriuni.  This  may  be  proved 
by  immersing  the  body  in  a  bath,  when  its  weight  is  found 
to  be  increased ;  and  not  only  water,  but  also  substances 
dissolved  in  it,  may  be  thus  introduced.  In  severe  cases  of 
dysphagia,  life  may  be  prolonged  by  the  use  of  nutritious 
enemata,  and  baths  of  milk  and  water,  beef  tea,  etc.  It  is 
in  this  way  that  the  iniodxis  operandi  of  liniments  may  be 
explained.  Certain  preparations  of  mercury  rubbed  in  the 
skin,  are  readily  absorbed  in  suflicicnt  quantity  to  affect 
the  system.  A  secretion  of  wateiy  fluid  or  perspiration  is 
continually  going  on  from  the  extensive  system  of  glands. 
It  generally  passes  off  in  the  form  of  vapour,  forming 
insensible  perspiration,  but  when  considerably  increased, 
the  fluid  remains  in  the  form  of  sensible  perspiration  on 
the  surface  of  the  skin.  The  perspiration  is  a  colorless 
watery  fluid,  of  an  acid  reaction,  and  has  a  peculiar  odor, 
which  varies  in  difl'erent  parts  of  the  body.  It  consists  as 
follows : 

Water 995-00 

Fatty  Matter  and  Cholesteiine .05 

Alkaline  Sulphates  and  Phosphates .05 

Sodium  and  Potassium  Chlorides 2.40 

Formic,  Acetic  and  Butyric  Acid 2.45 

Ammonia  (urea) .05 

Total 1000.00 

The  function  of  perspiration  is  to  regulate  the  tempera- 


INTEGUMENT. 


123 


tare  of  the  body.  The  natural  temperature  is  about  98°  to 
to  100°  F.,  and  a  variation  of  from  8"  to  9°  from  the  natural 
standard  usually  proves  fatal.  When  the  surface  is  exposed 
to  a  high  degree  of  heat,  the  glands  pour  out  an  increased 
amount  of  fluid.  This  is  immediately  converted  into  vapor, 
and  in  passing  from  the  liquid  to  the  gaseous  state,  so  much 
heat  becomes  latent  that  the  surface  is  cooled  down  to  the 
natural  standard.  When  the  air  is  dry,  so  that  evapora- 
tion is  not  interfered  with,  a  very  high  temperature — from 
300°  to  400°  F. — -can  be  borne  with  impunity  ;  but  if  the 
air  be  saturated  with  moisture,  evaporation  is  retarded,  and 
the  body  suffers  ;  and  if  the  exposure  be  long  continued, 
death  is  the  result.  The  amount  of  perspiration  may  be 
diminished  by  a  cold,  dam^  ,  atmo  phere,  and  increased 
by  heat,  exercise,  or  excitement.  The  quantity  of  fluid 
thrown  off  by  the  skin  varies  very  much,  according  to  the 
state  of  the  atmosphere  and  the  action  of  the  kidneys,  the 
average  amount  thrown  off  in  the  course  of  twenty-four 
hours  being  from  1|  to  2  pounds.  In  cold  weather,  when  the 
skin  is  less  active,  the  kidneys  take  on  increased  action, 
in  order  to  compensate  the  deficiency.  Whatever  tends  to 
prodi'.ce  dilatation  of  the  vessels  of  the  skin,  increases  the 
quantity  of  fluid,  and  con'  'action  diminishes  it.  Increased 
nervous  action  induces  copious  perspiration,  as  in  great 
excitement,  crises  of  disease,  night  sweats,  etc.,  and  any 
substance  which  will  allay  nervous  action,  as  atropine,  will 
diminish  the  amount  of  perspiration.  When  the  acf '  of 
the  skin  is  interfered  with,  as  in  burns,  scalds,  covering 
with  large  nlasters,  coating  with  varnish,  or  in  scarlatina, 
there  is  a  determination  of  blood  to  the  kidneys,  and  some 
of  the  albumen  escapes.  This  accounts  for  albuminuria  in 
the  exanthemata. 

An  interchange  of  gases  or  process  of  aeration  also  takes 
place  through  the  integument,  carbonic  acid  being  liberated 
and  oxygen  absorbed. 

A  most  important  function  of  the  skin  is  the  sense  of 
8 


1 

« 


124 


MEMBRANOUS  EXPANSIONS 


*<i 


touch.  This  varies  greatly  in  different  parts,  being  greatest 
at  the  extremities  of  the  fingers,  the  lips,  the  tongue,  and 
least  in  the  trunk,  arms  and  thighs.  Thus  the  two  points 
of  a  pair  of  conii)asses  rendered  blunt  may  be  separately 
distinguished  by  the  ])oint  of  the  finger  when  only  one- 
third  of  a  li?ie  apart ;  while  they  require  to  be  thirty  lines 
apart  to  be  separately  felt  on  the  integument  of  the  spine, 
arm,  or  thigh.  This  is  owing  to  the  unequal  distribution 
of  the  papilhv  uf  the  corium.  Parts  that  are  sensitive  to 
tickling,  as  the  axilhc  and  soles  of  the  feet,  are  com- 
paratively blunt  in  regard  to  the  appreciation  of  distance. 
Impressions  made  on  the  integument  continue  percei)tible 
for  a  considerable  time  after  tliey  have  been  removed,  as 
e.  (J.,  the  pressure  of  the  ring,  if  long  worn,  is  felt  on  the 
linger  for  some  time  after  its  removal,  and  is  apt  to  deceive 
the  individual. 

The  integument,  when  wounded,  is  not  restored  in  all  its 
integrity ;  the  cicatrix  ])resents  no  hair  follicles  or  glands, 
and  the  sensation  is  abnormal. 


DIGESTION. 


ur, 


CHAPTER  V. 


DIGESTION. 

Digestion  is  that  process  by  which  the  food  is  prepared 
fur  absorption  and  assimilation.  The  digestive  process  con- 
sists of  seven  ditierent  stages,  preheyision,  irMHti cation,  in- 
salivation,  decjlutltlon,  chymijication,  chylijication  and 
deftecation.  It  will  be  most  convenient  to  treat  of  tliese 
different  processes  in  their  order,  giving  the  mechanism  and 
the  changes  which  each  is  capable  of  effecting  in  the  food. 
Before  proceeding,  it  will  be  })rofitable  to  examine  the  vari- 
ous kinds  of  food  suitable  to  the  nourishment  of  the  hunian 
body. 

Food. — The/t>o(Z  of  man  consists  both  of  organic  and  in- 
organic substances.  The  best  classification  is  that  of  Dr. 
Prout,  in  which  the  different  kinds  of  food  are  divided  into 
four  groups  : 

1st.  The  Aqueous  Group. — This  forms  part  of  the  food 
of  ail  animals,  and  enters  largely  into  the  composition  of 
the  body. 

2nd.  The  Saccharine  Group.  —  This  group  is  derived 
chiefly  from  the  vegetable  kingdom,  and  comprehends 
sugars,  starch,  gums,  vinegar,  &/C.  They  consist  of  carbon, 
hydrogen  and  ox3'gen,  the  two  latter  in  the  pro[)ortion  to 
form  water. 

3rd.  The  Oleaginous  Group. — It  includes  oils,  fats  and 
alcohol.  They  resemble,  in  elementary  composition,  i\m 
preceding  group,  except  that  the  carbon  and  hydrogen  exist 
in  nearly  equal  proj)ortions. 

4th.  The  Witrogenous  or  Albuminous  Gr-oup.  All  srh- 
stances  belonging  to  this  group  contain  nitrogen,  as  fibr.j, 
albumen,  casein,  gelatine,  gluten,  etc.  They  are  chiefly  de- 
rived from  the  animal  kingdom.    Gluten  is  the  nitrogenous. 


! 
1 

«4 

:* 


120 


DIGESTION. 


Ill 'II 
i 

"■■IX 


principle  of  vegetables.  They  are  sometimes  called  hiato- 
fjenetic  aubatancea.  To  these  may  be  added  a  Mineral  or 
Saline  Group,  as  sodium  chloride,  calcium  phosphate,  etc. 

Milk  is  found  to  contain  ingredients  embraced  in  the  pre- 
ceding groups,  and  hence  it  is  well  adapted  to  the  growth 
and  development  of  the  young.  The  aqueous  group  is  rep- 
resented by  the  water,  the  saccharine  by  the  sugar  of  milk 
(lactose),  the  oleaginous  by  the  butter,  the  nitrogenous  by 
the  casein,  and  the  saline  group  by  sodium  chloride,  calcium 
phosphate,  etc.,  which  the  milk  contains.  From  the  above 
it  will  be  seen  that  the  food  of  man  is  naturally  subdivided 
into  two  great  classes ;  the  non-nitrogenous  embraced  in 
the  1st,  2nd  and  3rd  groups,  and  the  nitrogenous,  which 
embraces  the  4th  group  ;  the  former  supplying  a  large 
amount  of  carbon. 

Lie  big  styles  the  nitrogenous  substances,  the  plastic  ele- 
ments of  nutrition,  and  the  non-nitrogenous,  the  elements 
■of  respiration.  The  latter  term  is  objectionable,  however, 
inasmuch  as  those  substances  are  not  actually  required  in 
the  process  of  respiration.  The  terms  nutritive  for  the 
nitrogenous,  and  calorifacient  for  the  non-nitrogenous,  as 
proposed  by  Dr.  Thomson,  are  preferable,  or  the  terms 
hiatogenetic  and  calorijic.  In  colder  climates,  a  large  quan- 
tity of  the  calorifacient  elements  are  necessary  to  maintain 
the  proper  temperature  of  the  body,  and  the  natives  in- 
stinctively feed  on  fats  and  oils  ;  while  the  natives  of 
warmer  climates  feed  on  fruit,  which  contains  less  carbon. 

I'rom  the  construction  of  the  teeth,  and  digestive  appara- 
tus of  man,  a  mixed  diet  would  seem  to  be  the  most  suita- 
ble. Both  animal  and  vegetable  food  is  necessary  to  his 
highest  mental  and  physical  deveh^pment.  Certain  diseases 
may  arise  from  the  want  of  a  proper  admixture  of  fresh 
vegetable  diet,  as  scurvy.  This  is  due  to  the  absence  of  the 
vegetable  acids  in  the  system,  as  citric  and  malic  acid,  and 
itnay  be  remedied  by  their  administration  alone. 

If,  on  the  other  hand,  the  nitrogenous  elements  be  defi- 


FOOD. 


127 


cient  or  absent,  imperfect  nutrition  shows  itself  in  the  form 
of  ulcers  in  certain  parts  of  the  body,  as  in  the  cornea  and 
alimentary  canal  and  the  animals  die  of  emaciation.  Mag- 
endie  tried  the  experiment  by  feeding  dogs  for  some  time 
on  sugar  and  water  alone,  and  ulceration  of  the  cornea 
ensued.  The  same  rosults  were  observed  wlien  the  animals 
were  fed  on  gum  alone;  and  when  feed  on  olive  oil  and  watei*, 
or  butter,  the  animals  emaciated  rapidly,  but  ulceration  of" 
the  cornea  did  not  occur. 

Quantity  of  Food. — The  absolute  ([uantity  of  food  re- 
quired for  the  sustenance  of  the  body  in  health  varies  with 
the  age,  sex,  constitution,  habit,  and  the  circumstances  in 
which  the  individual  may  be  placed.  It  is  of  considerable 
importance  to  know  the  average  amount  of  food  required 
by  each  individual.  In  the  diet  scale  of  the  British  navy, 
each  seaman  gets  from  31  to  35^  ounces  of  dry  nutritious 
food  daily,  2f)  ounces  of  which  is  vegetable,  and  the  rest 
animal,  together  with  sugar  and  cocoa.  This  is  found  to  be 
amply  sufficient  for  the  support  of  strength.  The  soldier  is 
allowed  one  pound  of  bread,  and  one  pound  of  meat  per 
day,  with  vegetables  in  their  season,  and  tea,  coffee,  or  cocoa. 
In  the  English  hospitals,  full  diet,  upon  which  convalescents 
are  put,  consists  of  half  a  pound  of  meat,  twelve  to  fourteen 
ounces  of  bread,  half  a  pound  of  potatoes,  one  pint  of  milk, 
and  one  pint  of  beer,  or  half  a  pint  of  porter. 

In  prisons,  if  the  prisoners  are  idle,  they  receive  about 
25  ounces  of  solid  food  per  day,  5  or  6  ounces  being  meat. 
Some  persons  consume  large  quantities  of  food.  The  wan- 
dering Cossacks  of  Siberia  devour  from  8  to  20  pounds  of 
meat  daily.  It  has  been  ascertained  that  from  25  to  3"» 
ounces  of  solid  food  per  day,  one-fourth  of  which  should  be 
animal,  is  sufficient  to  maintain  health.  Prof  Dalton  esti- 
mates the  quantity  of  solid  food  necessary  for  a  healthy  man 
at  38|  ozs.  avoirdupois  per  day,  consisting  of  bread  19  ozs., 
meat  16  ozs.,  and  butter  or  fat  3|  ozs. ;  and  the  quantity  of 
water  at  52  fluid  ounces. 


It 


^ 


128 


DIGESTION. 


lit 
111 
« • 

n 


It  is  also  important  todGtorminc  the  proper  flict  suitable 
to  particular  nialailicH.  TIuih,  in  diaeaso  of  llio  kidneys, 
liver  or  bowrls,  or  in  rlioutnatism,  gout,  dy.spop.sia,  or  fatty 
<lo|)().sit,  nuicli  good  nuiy  bo  (^ti'ectod  l»y  a  well  regiilated 
dietetic  treatment.  For  example,  in  diabetes,  a  diet  of 
Auinuil  food,  and  the  avoidance  of  starch  and  sugar,  are 
generally  attended  by  good  results.  In  disease  of  the  liver, 
a  well-re<xulated  nitrownized  diet  is  njore  suitable  than  one 
abounding  in  carbon,  which  would  increase  the  work 
of  elimination  in  this  organ.  In  diarrluea  and  dysentery, 
bland  unstimulating  articles  of  food  should  be  used,  and  sub- 
stances containing  very  little  excrementitious  matter,  and 
easily  digested,  as  milk,  eggs,  beef  tea,  mutton  broth,  etc. 
Starch  and  sugar  are  bad  for  the  gouty,  rheunuitic  and  dys- 
peptic, for  they  are  transformed  into  fat,  lactic  acid,  and 
other  substances  in  the  system.  When  there  is  a  tendency 
to  obesity,  a  well  regulated  nitrogenized  diet  is  the  best 
adapted  to  obviate  it. 

Quality. — The  food  should  be  in  a  wholesome  or  unde- 
composed  state.  Those  who  are  in  the  habit  of  eating  de- 
composed food,  or  what  is  commonly  called  liaid  goiit — 
(highly  seasoned) — are  liable  to  zymoticdiseascs  and  disorders 
of  the  digestive  organs,  .as  diarrlui'a,  etc.  These  dif-eases  are 
very  prevalent  among  the  inhabitants  of  the  Faroe  and  Bird 
Islands,  who  are  in  the  habit  of  eating  what  they  call  "vast," 
half-decomposed,  maggoty  tiesh  and  fish.  Prize  fighters,  in 
training,  adopt  a  very  strict  regimen,  consisting  of  the  lean 
•of  beef  and  nmtton,  and  stale  bread,  together  with  about 
three  and  a  half  pints  of  fluid  per  day,  fermented  liquors 
being  strictly  prohibited.  Two  full  meals  are  allowed  with 
i\  light  supper  daily,  and  ])lenty  of  vigorous  exercise. 

Drink. — Water  constitutes  the  natural  drink  of  man,  and 
no  other  liquid  can  properly  supply  its  place.  The  average 
<|uantit\'  of  water  introduced  into  the  system  of  an  adult  in 
24  hours  is  about  50  ozs.;  therefore  its  purity  is  a  matter  of 
great  importance.     Water  conveyed  in  leaden  pipes  is  dan- 


gei 

\v 

wa 

th 

a  SI 

int 

dia 


otl 

scr 


DRINK. 


120 


<;oroiis,  in  conacqiicnco  of  the  formation  of  lead  carbonate, 
which  is  held  in  sohition  by  the  free  carbonic  acid  which  the 
water  contains.  Salines  in  excosr,,  produce  derangement  of 
tlie  digestive  organs ;  and,  as  in  the  case  of  deconij)OH'Ml  food, 
a  small  amount  of  putrescent  matter  in  the  water,  insi(iiously 
introduced  into  the  .system,  renders  it  liable  to  attacks  of 
diarrhcoa  and  to  the  inception  of  zymotic  diseases. 

The  use  of  alcohol  in  combination  with  water,  or  witli 
other  substances  in  the  form  of  fermented  Tupiors,  cannot 
serve  as  a  substitute  for  water.     It  precipitates  most  of  the 
organic  compounds  whoie  solution  in  water  is  nccessar}'  to 
their  assimilation.      It  cannot  sujjply  atiything  which  is 
essential  to  nutrition,  as  it  is  incapable  of  forming  albumin- 
ous compounds.    It  is  merely  useful  as  a  calorific  agent ;  but 
even  for  that  purpose  it  's  inferior  to  fats  and  oils.  It  is  also 
a  stimulant,  increasing  for  the  time  the  vital  activitv  of  the 
nervo-muscular  parts  of  the  body,  and  is  followed  by  a  cor- 
responding depression  of  power.     As  a  stimulant  it  is  use- 
ful in  low  forms  of  disease,  to  increase  the  digestive  process, 
to  raise  the  flagging  powers,  and  carry  the  patient  safely 
through  a  perilous  di>ease.     Beer  and  porter  may  also  be 
found  useful  in  various  forms  of  indigestion ;  the  bitter  prin- 
ci])le  which  they  contain  is  also  slightly  tonic  in  its  action. 
The  habitual  use  of  alcoholic  liquors  is  highly  injurious. 
They  are  poisonous  in  large  doses,  and  when  used  in  excess, 
produce  a  morbid  condition  of  the  nervo-muscular  parts  of 
the  body,  as  is  seen  in  delirium  tremen.s,  and  in  fatty  degen- 
eration of  the  muscular  tissues  of  the  body.     Intemperate 
persons   are    also    more    prone    to    epidcuiie    diseases,   as 
cholera,  dysentery,  fevers,  etc.,  in  consequence  of  the  accu- 
mulation of  effete  materials  in  the  blood,  which  render  it 
more  liable  to  "fermentation."     The  power  of  the  body  to 
endure  fatigue,  or  to  resist  the  extremes  of  heat  and  cold,  is 
also  diminished  by  the  use  of  intoxicating  liquors. 

Tea,  when  u.sed  in  moderation,  limits  the  less  of  weight 
when  the  diet  is  insufficient ;  prevents  the  loss  of  substance 


•I 
* 


130 


DICESTrON. 


4 

M 
V 


in  the  slmpo  of  uroa  ;  diiniuislics  V\v  amount,  of  prrspinition  ; 
and  lias  no  apprrciaMo  oH'rct  on  rospi ration  or  circMiIation  ; 
but  when  usod  iti  rxooss,  \h  stimulating  and  liigldy  injurious 
to  tijo  norvous  Hystom. 

CoFFKK  is  moro  stinuilatin^'  tlum  tt-a.  When  UHod  in 
modorati.'  quantities  it  prevents  waste  of  tlie  tissues,  arouses 
nervous  ener;j;y,  and  invij^oratt's  tho  circulation  ;  luit  in  ex- 
cess is  decidedly  injurious. 

ToHAcro,  tliouj^di  not  an  article  of  diet,  sliouhl  ho  referred 
to  in  this  connection,  as  in  excess  it  inti'rferes  very  nuich 
with  the  proper  assimilation  of  the  food.  •  Smoking',  chew- 
injjf,  and  snutHufj;,  are  lji(>  most  harliarous  customs  of  our 
race.  To  those  unaccustomed  to  th(»  use  of  tohacco,  it  causes 
nausea,  vondting  and  purging.  In  habitual  smokers  and 
cheweiN,  it  creates  thirst  and  increases  the  secretion  of  the 
saliva  anil  buccal  mucus,  which,  from  being  nnx<;d  with  th(! 
juice,  nnist  bo  expelled  from  the  mouth.  To  some  people 
tho  fumes  of  tobacco  are  very  disngreeable,  and  irritating  to 
the  lining  mendirano  of  tin;  lungs.  The  ajiplication  of  it  tu 
abraded  surfaces  is  very  dangerous,  and  has  been  known  to 
prove  fatal.  A  substance  called  </m>//>w  is  obtained  from 
tobacco,  which  is  very  poisonous,  almost  o(|ualling  in  activity 
hydrocyanic  acid. 

HUNOEU. — Hunger  is  the  jxeneral  want  of  nourishment  in 
the  system  ascribi'd  to  tho  stomach.  Tho  introduction  of 
food  into  tho  stomach  alone  will  not  allay  tho  sensation ;  it 
must  be  partially  absorbed,  and  enter  tho  circulation.  Hun- 
ger is  not  occasioned  by  more  emptiness  of  tho  stomacli  , 
neither  can  it  bo  duo  to  tho  secretion  of  gastric  juice,  as 
some  have  supposed,  because  that  fluid  is  not  secreted, 
except  during  digestion,  or  when  some  substance  is  intro- 
duced into  the  stomach.  It  is  more  ])robablo  that  the  sen- 
sation in  tho  stomach  is  duo  to  a  congested  condition  of  the 
capillaries,  beneath  tho  mucous  membrane,  excited  by  the 
influence  of  the  sympathetic  nerves,  and  communicated  or 
telegraphed  to  the  nervous  centre.     If  the  brain  is  actively 


STARVATION. 


ISl 


«!n<,'ajj;oil,  the  tulnj^rnplilo  iiit'ssa^o  is  not  noticcil,  nml  tlnm 
tho  scuHjition  may  Im!  ilispcllcMl  for  a  tiiiio.  hivi.sioii  of  *ho 
ptKMinidi^'astric  iiervt!  anniliilates  tlio  HoiiHatiori  of  satioty, 
but  tiot  of  lnmj'cr. 

TlHUHT. — Thirst  is  tho  ^'cncial  want  of  MuidH  in  the  hvh- 
toni  rofoncMl  to  tho  faucos.  This  wMisation  may  ho  as  offi.'ct- 
iially  allayo<l  hy  tho  iiitnxlnction  of  liciuids  into  the;  stonuicli 
as  hy  swallowing  in  tho  ordinaiy  way,  as  is  seen  in  casos  of 
cnt  thioat,  where  tin;  o'sophaj^ns  is  divided.  It  may  also 
ho  roliovod  hy  injoctiny  Ihiids  into  tho  veins,  or  hy  injinors- 
in<^  th(!  hody  in  a  hath. 

Stauvation  ok  Inanition.  —  This  is  tho  nssult  of  an 
entire  (h;Hci»!ney,  or  an  ina<h'(|iiato  supply  of  food.  In  star- 
vation the  V)ody  is  greatly  emaciated,  and  nsnally  (hsprivod 
of  its  adipose;  tissue.  TIkm'o  is  loss  of  weij^dit,  diminution  of 
temporatuiH!, general  weakness  and  hloodlessnoss.  The  most 
promintiut  symptoms  of  starvation  are,  first,  hunger,  which 
becomoK  paiid'ul,  the  pain  being  rel'errcd  to  tho  epigastric 
•ogion,  followed  hy  a  sinking  sensation.  Ne.\t,  an  insatia- 
•Die  thirst,  which  is  mo.st  distressing;  the  countenance  be- 
comes j»ah;  and  liaggai- 1,  the  (iyes  v/ild  and  glistening;  the 
body  exhales  a  peculiar  fetor,  tho  secretions  are  ottensive  ; 
the  hodily  strength  fails,  and  tho  voice  gets  weak.  The 
mental  powers  are  at  first  blurted,  and  the  sleep  consists  of 
short  naps,  disturbed  hy  dreams  in  which  tho  individual 
fancies  that  he  \\  in  sight  of  plenty  of  food.  Towards  the 
close  of  the  process,  delirium  generally  sots  in,  and  death 
closes  the  scene,  either  from  sheer  exhaustion  or  from  the 
occurrence  of  convulsions. 

Now,  it  will  he  observed  that  the  above  symptoms  are 
common  to  all  low  forms  of  disease;  and  the  medical  prac- 
titioner should  be  careful  in  such  cases  to  supply  nourish- 
ment and  stimulants  liberally ;  even  the  presence  of  delirium 
should  not  deter  him  from  administering  beef  tea  and  brandy. 

Life  may  be  supported  under  entire  abstinence  from  food 
or  drink  for  a  period  of  eight  or  ten  days  ;  but  this  period 
may  be  prolonged  by  the  occasional  use  of  water. 


1 

I* 

I 


WJriiMii 


132 


DIGESTION. 


<l| 


t.» 


III 


PREHENSION. 

The  organs  of  prehension  are  the  hands,  lips,  teeth,  and 
tongue.  The  tongue  is  used  in  suction,  somewhat  like  a 
l)iston,  so  as  to  produce  a  vacuum,  and  allow  the  fluids  tc 
enter  by  atmospheric  pressure.  Suction  cannot  properly 
take  place  when  the  tongue  is  tied  down  at  the  tip,  as  in 
tongue-tied  children,  it  being  necessary  that  the  tip  and 
sides  of  the  tongue  should  be  brought  in  contact  with  the 
roof  of  the  mouth.  In  drinking  a  fluid  by  means  of  a  sue- 
tion  tube,  as  a  quill  or  straw,  it  is  found  that  suction  will 
not  take  pUce  if  the  tube  is  passed  too  far  back  in  the  mouth, 
behind  the  floor  of  the  nares,  because  air  enters  through  the 
nose,  and  no  vacuum  can  be  produced.  The  tongue  of  some 
animals,  as  the  ant-eater,  is  covered  with  a  slimy  secretion, 
which  entraps  the  insects.  Dogs  and  cats  lap  the  water  by 
means  of  the  tongue. 


MASTICATION. 

This  is  the  first  process  which  the  food  undergoes,  and  is 
entirely  a  mechanical  one.  It  consists  in  the  cutting  and 
trituration  of  the  food  by  the  teeth.  The  principal  organs 
are  the  teetli,  tongue,  and  muscles  of  mastication. 

Teeth, — The  teeth  in  all  animals  are  suited  to  the  kind 
of  food  which  each  is  destined  to  use.  In  the  graminivora, 
some  of  the  teeth  are  formed  for  cutting  or  cropping  the 
food,  but  the  majority  of  them  are  broad  and  flat,  for  the 
purpose  of  grinding  it.  In  the  carnivora,  the  principal  teeth 
are  strong,  sharp,  and  pointed,  for  tearing  the  food,  while 
the  remainder  are  broad  and  flat.  The  teeth  of  man  partake 
of  the  nature  of  both  the  graminivora  and  carnivora,  as  he 
is  destined  to  feed  on  both  animal  and  vegetable  food.  In 
some  animals,  as  fish  and  reptiles,  which  swallow  their  food 
entire,  the  teeth  are  only  organs  of  prehension,  and  are 
curved  backwards  to  prevent  the  escape  of  their  prey.  Some 
of  the  lower  animals,  as  the  Crustacea,  are  provided  with 
teeth  in  the  stomach.    (For  structure  of  teeth  see  page  79). 


MASTICATION. 


133 


Tongue. — The  tongue  is  an  important  organ  of  mastica- 
tion, and  being  the  seat  of  taste,  it  receives  accurate  impres- 
sions of  the  kind  and  quality  of  the  food.  While  the  food 
is  being  triturated,  the  tongue  is  engaged  in  moving  it  from 
side  to  side,  in  collecting  the  scattered  fragments  from  dif- 
ferent parts  of  the  mouth,  and  bringing  them  within  the 
range  of  the  teeth.  This  action  is  accomplished  by  the 
muscles  which  belong  to  this  organ.  The  cheeks  also  assist 
more  or  less  in  moving  the  particles  of  food,  and  keeping 
them  within  the  ranfje  of  the  teeth. 

The  muscles  of  mastication  are  the  temporal,  masseter, 
external  and  internal  pter^^goid,  and  digastric.  The}-  all 
act  upon  the  lower  jaw,  which  is  capable  of  being  moved  in 
different  directions,  for  the  purjjose  of  triturating  the  food. 
The  temporal,  masseter  and  internal  pterygoid  elevate  the 
lower  jaw,  and  close  the  mouth.  The  posterior  fibres  of  the 
temporal  and  the  deep  part  of  the  masseter  carry  it  upwards 
and  backwards.  The  extei-nal  and  internal  pterygoid,  and 
superficial  part  of  the  masseter,  draw  it  upwards  and  for- 
wards. Botb  pterj'goids  draw  it  from  side  to  side,  and  it  is 
depressed  by  the  action  of  the  digastric  muscle. 

The  contour  and  structure  of  the  temporo-maxillary  arti- 
culation are  well  adapted  to  the  performance  of  these  various 
movements.  The  presence  of  a  plate  of  inter-articular  tibro- 
cartilage  serves,  by  its  elasticity,  to  distribute  the  pressure 
caused  by  the  action  of  these  muscles.  It  also  gives  ease  to 
the  gliding  movements,  and  serves  as  a  socket  for  the  condyle 
of  the  lower  jaw,  when  the  latter  is  drawn  forwards  by  the 
external  pterygoid  muscle.  Some  of  the  fibres  of  this  mus- 
cle are  attached  to  the  anterior  margin  of  the  plate  of  carti- 
lage. 

Mastication  is  partly  voluntaiy,  and  also  partly  re- 
flex or  involuntary.  The  principal  nerves  concerned  are 
the  sensory  branches  of  the  fifth  and  the  gl()SSo-[)haryngeal, 
and  the  motor  branches  of  the  fifth  and  ninth  cerebral  nerves. 


1 
t 

J 

It 


in  I. 


n/G/CSTfON. 


-  * 

!! 


tNHAI.lVATrON. 

T\n)  lotxl  in  its  passniu^i*  fVom  abovo  downwards  is  actod 
upoti  by  (ivo  (bUcrcnl  Ibiids,  \\7..,  Hdiiva,  (faHtric  juice,  in- 
fesfimil  Juice,  )uiv<'r(><itiv,  jiiice,  M\{\  bile,  onc\\  of  which  is 
of  a  nioro  or  U^ss  (•oin{>lox  luituiv.  Dining  the  |)1'oc(\sh  of 
\iiiuslioation,  iho  foo»l  is  mixiMl  with  tho  saliva..  This  sub- 
stanco  is  a  mixtun^  of  four  «liM(,inct  Ibiids  which  differ  from 
«»ach  otlicr  in  (l»(Mr  cluMuical  and  physical  pioptMlics,  viz.: 
tho  .secretion  of  th(»  parotid  }^land,  (he  submaxillary,  the 
snblinjvunl,  and  tho  buccal  glands.  The  parotid  gland  is 
situated  luMHVith  (he  ear,  dost;  to  the  teuiporoniaxillary 
articulation,  and  opens  into  the  mouth  by  its  ««xcr<>tory 
duct  (^Steno's\  opposite  the  second  mohir  tooth  of  (,h(^  upper 
jaw.  The  submaxillary  ijlaml  issi(ua(ed  b«>neath  the  lower 
jaw,  and  comnnn\ica(t>s  wi(h  the  niou(.h  through  Wharton's 
duct,  which  •  ens  on  the  side  of  the  IYmmhuu  linguie.  The 
sublingual  gland  is  situa(.(>d  beneath  the  (t)ugu(»,  near  tho 
symphysis  of  the  lower  jaw,  atul  opens  into  th(»  mouth  upon 
an  clevatcMl  civst  o\'  mucous  metnbraui*  (^which  may  \h)  felt 
by  tl)e  tip  o\'  the  tongui*),  by  tifteen  or  (wenty  opcMiings 
(ductus  UivinianiY 

Stiutotuuk  ok  thk  S.M.iVAKV  (iT,ANi)S. — Th(>  salivary 
glands  consist  of  numerous  lobes  made  up  of  smaller  lobides 
connecteil  together  by  anM)lar  tissue,  vessels,  nerves,  otc. 
Kiaeh  l(>bule  c«>nsists  of  numerous  vesicular  pouches,  or  (rei)il 
wliich  open  into  a  ct)mmon  duct  ;  these  vesicular  })ouches 
are  about  j^l^  of  an  inch  in  diauu^ter  (">()  nunm.)  lined  by  a 
layer  of  roumled  or  glandular  epithciium,  and  surroumled 
by  capillaries  and  nerves.  The  cells  wliicli  line  tho  pouches 
and  ducts  are  smaller  than  those  which  secrete  tho 
saliva.  The  secretion  of  saliva  is  stiujulated  by  tho  pre.sonco 
of  food  or  otlier  substances  in  tho  mouth  ;  oven  tho  aiglit  or 
idea  of  food,  or  it<s  presonco  in  tho  stomach,  causes  tho  mouth 
to  "  water."  At  other  times  tho  accroti()n  is  very  limitt^d 
in  quantity.     The  amomit  secreted  in  twenty-four  liours  is 


m 


''^^a^ggg' 


INSAr.IV/niON.  135 

varionwly  ('Htirnatoil  \\X,  from  ono  to  tlire(5  poiindH  avoinlu- 
jioiH. 

Saijva. — Saliva  in  a  Hli^'lit,!/  viscnl,  fcmiiH[)aroTit  fluid, 
<loi»(»Hit,in^,  »)n  staiidiii^,  a  litl.li;  (btccnlcnt  HijdiiiKtnt,  conniHt- 
iiifT  |»iinci|ially  of  Hcaly  (j|»itliolitnii  of  tlio  inoiiili,  Httiall 
tmol(!at(Ml  (M'IIh  IVoiii  tlio  ^landn  oi-  ductH,  ^laiinlar  inaitoi', 
afid  oil  globulus.  I(h  Hpccilic;  gravity  in  about  1005;  UHiially 
allvalinn,  Imt  oltcn  luMitnil,  atid  HoiiK.'titrn^H  Kli^^ditly  acid  in 
its  roactioii.  It  in  ulkaliiu!  during  digcistion  ;  and  neutral 
during  lasting  (»vving  to  a<lniixturo  with  the  acid  uiucouh  of 
tho  mouth. 

Composition  ok  Samva. — (Uiddcr  tV,  Solwnidt) : 

Water 995. 16 

Oif^iiiiic  niadcr,  (|>lynlin  or  saliviii) I.34 

I'i>t!issiiiiii  SmI|)1u)(  ynniilo ,06 

('alcium,  scidiiiiii  and   inaf;n(!>,ium    pliosphatfs.  .9S 

Sudiimi  and  |)i)lassiiim  idiloiidc:-.    .X4 

Kpilliditiin  and  ^land  cells 1.62 

I  OCX).  00 

It  is  al.s(»  .said  to  contain  a  trac(3  of  an)unu!n,  and  soinc  oil 
globules  ;  it  thorcl'oro  becoinuH  slightly  turl)id  on  boiling,  or 
l)y  tho  addition  (»f  nitric  acid.  Tlu!  pi nallii  gives  the  saliva' 
its  vi.sci<lity  ;  it  is  coMgidated  by  al<;ohoI,  but  not  by  luiat. 
PotaHsiuni  sulj)hoc3'anido  may  be  detected  by  iron  chloiido, 
which  produces  the  characteii.stic  red  color  of  iron 
sulphocyanide. 

The  saliva  from  tin;  ])arotid  gl  uid  is  a  clear,  limpid, 
watery  fluid,  having  a  distinctly  alkaline  reaction.  It  may 
bo  readily  obtaiiuMl  by  introducing  a  silver  canula,  2',,  of  an 
inch  in  diameter,  into  tho  orifice  of  Steno's  <Iuct,  The  quan- 
tity of  organic  matter  in  the  parotid  .saliva  is  large,  when 
compared  with  tho  mineral  ingredients.  The  submaxillary 
saliva  di tiers  from  the  parotid  secretion  in  being  somewhat 
viscid,  and  more  strongly  alkaline.  It  may  bo  sccurtsd  by 
inserting  a  canula  into  Wharton's  duct,  The  saliva  from 
the  sublingual  gland  is  also  alkaline,  and  more  viscid  than 
the  j)receding. 


« 
1 

t 


13G 


DIGEST/ON. 


The  secretion  from  the  buccal  glands  and  mucous  mem- 
brane is  obtained  by  ligating  the  ducts  of  the  parotid,  sub- 
maxillary, and  .sublin<]rual  glands,  to  exclude  their  secretion, 
and  then  collecting  the  fluid  subst^quently  secreted  in  the 
mouth.  This  fluid  is  small  in  quantity,  aiid  much  more 
viscid  than  either  of  the  preceding  secretions. 

Function  of  Saliva. — It  possesses  the  property  of  con- 
verting boiled  starch  into  dextrin  and  sugar,  if  kept  in  con- 
tact wivh  it  a  short  time,  at  the  teuipeiutui-e  of  38"  (100° F.) 
This  amytoli/tic  action  is  due  to  the  presence  of  the  organic 
matter  or  ptyalin  which  acts  as  a  ferment.*  This,  there- 
fore, was  formerly  su|>posed  to  be  the  true  physiological  use 
of  saliva,  viz.  :  to  dissolve  or  digest  the  starchy  portions  of 
the  food.  It  was  very  soon  noticed,  liowever,  that  in  the 
ordinary  process  of  digestion  the  starchy  matters  do  not  re- 
main long  ej.ough  in  the  mouth  for  this  change  to  take 
place,  but  pass  at  once  into  the  stomach,  where  ilie  further 
conversion  of  starch  into  sugai'  is  retarded  by  the  presence 
of  the  gastric  juice.  The  most  important  use  of  the  saliva 
is  to  moisten  tlie  food  and  facilitate  its  mastication,  to  lubri- 
cate the  mass  or  bolus,  and  to  assist  in  its  pas.sage  during 
the  process  of  deglutition.  The  wateiy  fluid  of  the  parotid 
gland  is  useful  in  the  process  of  mastication  ;  while  the 
more  viscid  secretion  of  the  other  glands,  and  buccal  mucus, 
serve  to  lubiicate  the  triturated  mass,  and  facilitate  its  pas- 
sage down  the  oesophagus.  The  tonsils  also  secrete  a  viscid 
fluid,  which  serves  to  lubiicate  the  bolus  of  food  during 
swallowing.  During  mastication,  the  saliva  is  intimately 
mingled  with  the  mass,  and  may  in  this  way  mechanically 
enable  the  gastric  juice  to  penetrate  more  readily  every 
part,  as  it  enters  the  stomach.  It  was  observed  by  Spallan- 
zani  that  food  enclosed  in  perforated  tubes,  and  introduced 


♦There  are  two  classes  of  ferments,  organized  and  unorganized.  The  action 
of  the  former  is  dependent  on  the  life  of  the  ferment,  as  for  example  the  yeast 
plant  whose  fermentative  activity  depends  on  the  life  of  the  yeast  cell  ;  the 
latter  is  not  a  living  organism. 


DEGLUTITION. 


137 


into  the  stomachs  of  living  animals,  was  more  readily 
digested  when  previously  mixed  with  saliva,  than  when 
mixed  with  water.  The  salivary  glands  are  not  very  acuivc 
in  infants  until  the  age  of  six  months,  and  they  are  there- 
fore incapable  of  properly  digesting  starchy  food,  corn 
flour,  etc. 


DEGLUTITION. 

The  organs  of  deglutition  are  the  mouth,  tongue,  pharynx, 
and  oesophagus.  The  mechanism  of  deglutition  may  be 
divided  into  three  stages.  In  the  first  the  food,  when  pro- 
perly masticated,  is  formed  into  a  bolus  on  the  tongue,  and 
carried  backwards  through  the  anterior  pillars  of  the  fauces, 
by  that  organ,  and  forced  into  the  pharynx.  This  is  done 
by  the  pressure  of  the  tongue  against  the  roof  of  the  mouth 
— the  pressure  commencing  at  the  apex,  and  ending  near 
the  base.  During  the  second  stage,  the  hyoid  bone  is  car- 
ried upwards  and  slightly  forwards  by  the  anterior  belly  of 
the  digastiic,  mylo-hyoid  and  genio-hyoid,  the  pharynx  is 
raised  by  the  stylo-pliaryfigeus  and  palato-pharyngeus  to 
receive  the  bolus,  the  epiglottis  is  pressed  over  the  aperture 
of  the  larynx,  by  the  elevation  of  the  pharynx  and  larynx 
towards  the  base  of  the  tongue,  and  the  bolus  glides  past. 
The  baso  of  the  tongue  is  now  diawn  slightly  upwards  and 
backwards  by  the  posterior  belly  of  the  digastric  and  stylo- 
hyoid, the  palato-glossi  (or  constrictors  of  the  fauces)  con- 
tract, and  prevent  the  return  of  the  bolus  into  the  mouth, 
the  soft  palate  is  raised  by  the  levator  palati,  the  ])alato- 
pharyngei  contract  and  come  neaily  together,  the  uvula 
tilling  u})  the  space  between  them,  and  in  this  way  the  food 
is  prevented  from  passing  into  the  posterior  nares.  In  the 
third  stage,  the  constrictors  of  the  pharynx  contract  upon 
the  bolus  from  above  downwards,  and  force  it  into  the 
oesophagus,  which,  by  virtue  of  its  peristaltic  action,  urges 
it  onwards  to  the  stomach.  The  first  act  is  voluntary  ;  the 
second  and  third  are  involuntary.     The  nerve  centre  for 


1 


138 


DIGESTION. 


n. 


t..:  U 


<leglutition  is  the  medulla  oblongata ;  the  nerves  concerned 
in  the  act  are,  the  sensory  branches  of  the  rifth,  glosso- 
]>haryngeal  and  ]ineuniognstric  nerves,  and  the  motor 
branches  of  the  fifth,  facial,  hypoglossal,  pneumogastric  and 
sj)inal  accessory. 

Vomiting. —  In  the  mechanism  of  vomiting,  the  jirocess 
of  deglutition  is  exactly  reversed.  This  may  be  cau.sed  by 
the  administration  of  direct  or  indirect  emetics,  by  mental 
emotion,  as  the  sight  of  a  disgusting  object,  by  any  unusual 
motion,  as  sailing,  swinging,  »Jcc.,  by  nervous  shock,  as  in 
the  case  of  severe  wounds,  by  derangement  of  the  sy.stem, 
or  the  ])resence  of  irritating  substances  of  any  kind  in  the 
stomach,  or  obstruction  to  the  ])as.sage  of  the  food  through 
the  bowels.  Its  rationale  may  be  explainetl  by  the  theory 
of  reflex  action.  The  irritation  or  impression  being  applied 
to  the  periphery  of  the  nerves,  is  first  conveyed  to  the 
nervous  centres  (uiedulla  oblongata),  and  thence  a  motor 
impulse  proceeds,  l)y  which  an  impression  is  made  upon 
those  j)arts  concerned  in  tlio  act  of  vomiting,  through  the 
nerves  which  are  distributed  to  Ihem.  The  medulla  oblon- 
gata may  be  affected  direcily  by  the  presence  of  particular 
substances  in  the  blood,  or  causes  acting  directly  on  the 
centre  itself  The  motor  nerves  implanted  in  it  are  thus 
stimulated  to  action,  and  the  abdominal  muscles,  diaphragm, 
nmscles  of  the  larynx  and  pharynx,  as  well  as  the  muscu- 
lar fibres  of  the  stomach  or  (vsophagus,  are  thrown  into 
contraction. 

First,  a  deep  inspiration  is  taken  ;  the  aperture  of  the 
glottis  is  closed,  and  the  lungs  being  filled  with  air,  the 
diaphragm  is  fixed.  The  glottis  is  closed  by  the  elevation 
of  the  larynx  against  the  base  of  the  tongue.  The  pharynx 
is  raised,  the  palato-pharyngei  contract  and  close  the  pos- 
terior nares,  the  uvula  filling  the  small  interval  between 
them,  and  thus  the  fluids  are  })revented  passing  through 
the  nose.  This  constitutes  the  first  act.  Then  the  stomach 
contracts  and  is  compressed  against  the  diajihragm  by  the 


CHYMIFICA  TION. 


130 


contraction  of  the  abdominal  muscles  ;  the  pylorus  is  closed, 
and  the  contents  are  forcibly  ejected,  their  passage  being 
facilii.ited  by  the  anti-peristaltic  action  of  the  stomach, 
ccsophagus  and  pharynx. 

CIIYMIFICATION. 
This  ])rocoss  takes  place  in    the  stomach,   throu<^h  the 
agency   of  the  gastric  juice.     The  walls  of  the  stomach 
consist   of  three   coats;   an    ext(!rnal    peritonc^al  or  serous 
membrane;  a  middle  muscular,  consisting  of  longitudinal, 
circular  and  obli(iue  fibres  ;  and  a  mucous  coat;  with    ves- 
sels, nerves  and   lymphatics,  all   held   together   Vty   areolar 
tissue.     A  delicate  form  of  connective  tissue  is  found  in,  or 
immediately  beneath  the  mucous  membrane,  called  reticu- 
lar or  retiforin  tissue,  the  meshes  of  which  contain  lymph 
corpuscles.     There    are    also    some    noustriated    muscular 
fibres  called  muHCularis  mucoHW.     The  mucous  membrane 
of  the  stomach  is  lined  by  columnar  epithelium,  and  when 
examined  by  a  lens,  it  presents  a   ])eculiar  honeycombed 
api)earance,  caused  by  a  number  of  shallow   depressions  or 
alveoli  of  a  polygonal  or  hexagonal  form,  which  vary  from 
TOO  t')  a  Jo  of  an    inch  in    diameter,   separated    by   slight 
ridges.     In  the  bottom  of  each  alveolus  may  be  seen  the 
orifices    of  minute   tubes,    the   gastric  follicles.     Tliey  are 
arranged  per[)endicularly,  side  by  side,  short,  and   tubular 
in  character  towards  the  cardiac  end  ;  but  near  the  pyloric 
extremity,  they  are  more  thickly  set,  convoluted,  and  ter- 
minate in  dilated  saccular  extremities,  or  divide   into  from 
two  to  six  branches,  the  object  of  which  is  to  increase  the 
extent  of  surface  for  secretion  (Fig.  -iS).     The  follicles  con- 
sist of  an  involution  of  the  basement  membrane,  lined  with 
cells,  and  are  divided  into  two  varieties,  which  differ  only 
in  the  character  of  the  cells  which  line  them,  and  the  secre- 
tion   which    they   produce,  viz :  the  mucoivs  follicles  and 
peptic   follicles.     The    former    predominate    towards    the 
pylorus,   and    the    latter   towards    the   cardiac    end.     The 
9 


f 

.4 


140 


nraESTioiv. 


♦I 

i-: 


imic<MiH  folliclos  RYo  litiod  with  coltiinnar  opitliolitiiti  on  Mio 
sidos,  and  nnnulod  in  tho  bottom,   and  socicto   i\w  niucuH. 
Tlio  deep   part  of  the    poptic   tolliolo   is  filKMl   with    lar^ro 
gmnniar  sph(>roidal  wWh  ;  abovo  this  it  is  lin(»d  liy  round(Ml 
opitholiuni,  and  tho  upper  part  of  tiio  follicle  is  lined  with 
onlinary  cohunnar  epitheiinni.     These  follicles  are  snpi)osed 
to  secrete  the  gjistric  juice.     n(!sid(»s  these,  there    are  tho 
lenticuldv  ijlauds,  which  resemble  in  structure,  function  and 
general    ajipearanco,  the  solitary   glands  of  tho  intestine. 
They  are  situated  beneath  the  surface  of  the  mucous  mem- 
brane, and  are  found  chiefly  along  the   lesser  curvature  of 
the  stonuich.     The    mucous    membrajie  of  the  stomach  is 
abundantly  supplied  with    blood-vessels.     'I'hese    break  up 
into  fine  capillary  plexuses,  with  oblong  meshes,  which  sur- 
round the  follicles,  and  are  prolonge*!  upwards  to  the  ridges 
of  nnicous  membrane   boimding  the   pits  or  alveoli.     The 
nerves  of  tl)e  stonuieh  are  derived  from  the  pneumogastric 
and  .sympathetic.     In  the  submucous  areolar    ti.ssue  of  tho 
stomacli   and    intestines,  there  is   a   fine    plexus   of  non- 
medullated  nerve  fibres,  known  as  "  Mei.ssner's  plexus." 

Gastric  .Tuiok. — (histric  juice  was  obtained  by  Spallan- 
zani  from  the  stonuichs  of  aninials,  by  causing  them  to 
swallow  sponges,  attached  to  the  end  of  a  cord,  by  which 
they  were  afterwards  withdiawn  and  the  fluid  expressed. 
It  has  since  been  obtained  and  experimented  upon,  by  Dr. 
Beaumont,  of  the  U.  S.  Army,  from  Alexis  St.  Martin,  a 
Canadian  boatman,  who  had  a  permanent  gastric  fistula, 
the  result  o(  a  gun-shot  wound.  Schmidt  has  also  had 
opportunities  of  examining  it  in  a  female  named  Catherine 
Kutt,  who  had  for  three  years  a  gastric  fistula  under 
the  left  nuinnnary  gland.  It  nu\y  also  be  obtained  from  any 
of  the  lower  animals,  by  nuiking  an  artificial  opening 
through  the  abdominal  walls  and  inserting  a  canula. 

Physical  ArrKARANCE  and  Propkrtiks — It  is  a  clear, 
colorless  fluid,  of  an  acid  reaction,  secreted  only  during 
digestion,  or  as  the  result  of  some  irritation  applied  to  the 


Tl 


GASTRIC  JUICE.  Ul 

iinicoiis  coat  of  tl)(5  Htomaoli.  Its  specific  jrjavity  vnriow 
from  1001  to  lOlO.  It  is  not  proiKs  to  decomposition,  and 
may  Ih;  kept  for  an  indefinite  length  of  time  in  an  ordinary 
glass-stoppered  bottle.  After  stan<ling  for  two  or  three* 
W(M'ks,  a  (!onf(^i  void  vegctaldc  growth  sliows  itself  in  the 
finid.  This  growth  has  a  dendritic  appearance,  each  branch 
or  filament  consisting  of  a  single  row  of  el<»iigat«Ml  cells. 
The  total  cpiantity  of  gastric;  jniec  secreted  in  twcnty-foiir 
hours  is  from  tisn  to  twen:y  pifits  (Firinton).  This  would 
seem  almost  incredihle,  did  we  not  remember  that  the 
gastric!  juic(^  is  in  j)ait  realtsoibed,  together  with  tho 
alimentaiy  substanc<\s  which  it  holds  in  solutiotj,  after  tho 
process  of  digestion  is  completed.  The  secretion  of  gastric 
juice  is  nujch  influenced  by  nervous  conditions.  It  in 
diminislKul  l>y  irritation  of  temj)er,  f«;ar,  joy,  fatigue,  mental 
exertion,  or  any  febrile  distuibnnce  of  the  system.  The 
gastiic!  juice  does  not  act  on  the  nmcous  mend)rane  of  the 
stomach  during  life  ;  but  r.fter  death  this  menibrane  is 
generally  found  dissolved  and  disintegrated  by  its  action 
This,  according  to  I'avy,  depends  upon  th(!  alkalinity  of  tin? 
the  blood,  which  circulates  fret.'ly  during  life  in  tho  walls 
of  the  stomach,  and  which  neutiali/es  the  acidity  of  tho 
gastric  juice  an«l  destroys  its  digestive  powers  on  the  coats 
of  the  stomach. 

CHKMICAL   (JOMPOSITION    OF   GaSTRIC  JuICE: 

numan.  Dog's. 

Water 994-40  97'-  '7 

l'oi)sinc 3-'9  '7-SO 

Hydrochloric  acid,  (free) 0.22  2.73 

Sodium,  potas'iium,  and  calcium,  chlorides  ....        2.07  5.87 

Magnesium,  calcium  and  iron  Phosphates 12  2.73 

Traces  of  Ammonia 

lcX).oo  100.00 

It  was  formerly  supposed  that  lactic  acid  was  the  acidify- 
ing agent  of  the  gastric  juice,  and  in  all  probability  a  small 
quantity  is  sometimes  present ;  but  hydrochloric  acid  is 
much  the  more  abundant  and  important  of  the  two.     The 


1 
f 

M 
A 

\ 

It 

\ 


142 


DIGESTION. 


c 
II, 


presence  of  free  acid  is  essential  to  its  ])hysiological  proper- 
ties, for  the  gastric  juice  will  not  exert  its  solvent  action 
upon  the  food  after  it  has  been  neutralized  by  an  alkali. 

The  organic  matter,  or  pepsine,  is  next  in  importance.  It 
is  precipitated  from  its  solution  in  the  gastric  juice  by  alco- 
hol and  various  metallic  salts  ;  but  is  not  affected  by  potas- 
sium ferrocyanide.  It  may  be  coagulated  by  boiling.  Gas- 
tric juice  which  has  been  boiled,  or  mixed  with  a  small 
■quantity  of  bile,  loses  its  property  of  digesting  substances. 

Function. — It  dissolves  the  albuminoid  or  nitrogenous 
substances  (proteids)  of  the  food,  and  converts  them  into  a 
substance  called  albuminoso  or  peptone.  The  licpiofying 
process  which  the  lood  undergoes  in  the  stomach  is  thought 
b}'  .some  to  be,  not  a  sim])le  solution,  but  a  catalytic  trans- 
formation produced  in  the  albuminoid  substances  by  the 
pepKine,  which  acts  as  a  ferment  (hydrolytic).  The  gastric 
juice  will  exert  its  solvent  action  on  the  food  outside  the 
body,  as  well  as  in  the  stomach,  if  kept  in  glass  phials  upon 
a  sa!ul  bath,  at  a  temperature  of  100°  F.  In  the  digestion 
of  cooked  meat,  the  gastric  juice  first  dissolves  the  areolar 
tissue,  and  thus  sets  free  the  muscular  fibres,  which  aie  sub- 
sequently acted  upon  and  dissolved.  Some  albuminoids,  as 
casein  of  milk  are  first  coagulated  by  the  action  of  the  gas- 
tric juice,  and  then  acted  upon  similarly  to  the  other  solid 
principles.  The  albuminoid  or  proteid  substances  are  acted 
upon  so  as  to  be  changed  into  albuminosc  or  peptone.  This 
substance  differs  from  ordinary  albumen  in  not  being  |)reci- 
pitated  by  heat,  nilric  or  acetic  acid,  or  potassium  ferroc^'an- 
ide,  and  in  being  rendered  di fusible,  or  easily  absoibed. 
It  is  readily  precipitated  by  tannic  acid  or  hydrargyrum 
perchloriclg.  The  peptones  are  closely  allied  to  the  crystal- 
loids,which  possess  superior  osmotic  ])roperties  as  compared 
with  the  colloids.  Some  authors  describe  three  sorts,  a,  b, 
and  c,  peptones;  other  allied  substances  formed  during 
digestion  are  named  parapeptone,  metapeptone,  and  dyspep- 
tone.      After  entering  the  blood  vessels,  the  peptones  are 


RATE  Of   DIGESTION. 


14S 


again  transformed  into  all>innen,  a  change  wliich  is  neces- 
sary lo  prevent  their  passing  out.  The  saccharine  portions 
of  food  arul  dextrine  are  at  once  absorbed  in  tlie  stomach. 
Tlie  amylaceous  principles  are  prepared  for  the  action  of  the 
pancreatic  juice,  by  softening  the  external  covering  of  the 
starch  granules.  Fatty  ti.ssues  are  also  partly  disintegrated 
and  the  fatty  matter  set  free,  by  a  solution  of  the  areolar 
tissue  and  albuminous  cell  walls,  but  tl.  j  fat  itself  undergoes 
no  change.  The  gastric  juice  also  possess  ant'iHeptic  pro- 
perties, which  not  only  prevents  the  putrefaction  of  nitro- 
genous substances  during  digestion,  but  also  corrects  the 
effects  of  partly  decomposed  substances  taken  as  food. 

Influence  of  the  Neuvous  System  on  Diuestion. — 
The  function  of  digestion  is  arrested  by  strong  mental  emo- 
tion or  serious  bodily  injuries,  and  the  food  is  often  rejected. 
The  moveinents  of  the  stomach  are  due  to  the  presence  of 
food  acting  as  a  stimulus  to  the  periphery  of  the  nerves, 
transmitted  to  the  ganglia,  and  reflected  to  the  muscular 
coat.  Irritation  of  the  pneumogastric  nerves  produces  in- 
creased peristaltic  action  of  the  stomach,  and  division  retards 
or  arrests  it,  and  temi)orarily  arrests  the  secretion  of  gastric 
juice.  Galvanization  of  these  nerves  increases  the  secretion 
of  the  fluid,  but  diminishes  it  when  applied  to  the  sympa- 
thetic. 

Rate  of  Digestion. — The  time  required  for  digestion 
varies  in  different  animals.  In  the  carnivora,  fresh  raw 
meat  requires  from  nine  to  twelve  hours.  The  average  time 
required  in  the  human  subject  varies  from  one  to  Ave  and 
a  liPvif  hours,  according  to  the  nature  and  quantity  of  food 
taken. 

Dr.  Beaumont's  table,  taken  from  Alexis  St.  Martin. 


Pigs'  Feet i.cx)  hour. 

Tripe   i.cxj     " 

Trout 1.30     " 

Venison   1.35     " 

Milii 2.00  hours 

Roast  Turkey 2.30     " 


Roast  Beef 3.00  hours. 

Roast  Mutton 3.15      " 

Veal 4.00      " 

Salt  Beef 4.15      " 

Roast  Pork  5. 15      •* 


A 

1 

It 


144 


DIGESTION. 


•  ■lit 

It: 
ft. 


Artificial  Digestion. — An  artificial  digestive  fluid  may 
be  made  by  macerating  portions  of  the  mucous  membrane 
of  a  fresh  stomach  in  water  or  glycerine,  or  by  dissolving  pep- 
sine  in  water  and  then  adding  hydrochloric  acid  (1  part  in 
1000.)  The  fluid  thus  formed  will  digest  portions  of  food 
if  kept  at  a  temperature  of  98  to  100°  F.  Such  a  prepara- 
tion is  very  useful  in  cases  where  deglutition  is  impractica- 
ble, and  in  which  the  body  is  being  nourished  by  nutritive 
enemata.  It  is  mixed  with  the  nutritive  fluid,  whicli  is  in- 
jected into  the  bowels.  7-'cp8i'>*e  is  administered  with  benefit 
in  some  forms  of  dyspepsia,  but  should  be  combined  with 
hydrochloric  acid. 

Movements  of  the  Stomach. — These  are  effected  by  the 
alternate  contraction  ot  the  longitudinal  and  circular  flbres 
of  its  muscular  coat.  The  muscular  fibres  of  the  orifices 
also  keep  the  stomach  closed  during  digestion.  The  move- 
ments were  observed  by  Dr.  Beaumont,  in  the  stomach  of 
Alexis  St.  Martin  by  introducing  the  stem  of  a  thermometer. 
This  action  is  more  energetic  near  the  pylorus,  the  bulb 
being  grasped  tightly  and  drawn  towards  this  orifice.  The 
peristaltic  action  of  the  coats  of  the  stomach  produces  a  kind 
of  double  current  of  its  contents,  the  circumferential  portions 
being  moved  towards  the  pylorus,  while  the  central  portions 
are  propelled  in  the  opposite  direction,  towards  the  cardiac 
orifice.  The  action  of  the  stomach  produces  a  constant 
movement  of  the  food,  and  secures  its  thorough  admixture 
with  the  gastric  juice,  which  peneti'ates  ever}'  particle,  and 
converts  it  into  a  greyish  pulpy  mass  of  a  homogeneous 
a])pearance,  called  chyme,  which  then  passes  into  the 
duodenum. 


CHYLIFICATION. 


This  process  takes  place  in  the  small  intestine,  but 
principally  in  the  duodenum.  For  a  description  of  the 
niucous  membrane  of  the  small  intestine,  see  "raucous 
membranes."     It   has  already  been  stated   that   only   the 


INTESTINAL  JUICE. 


145 


albuminoid  subHtances  are  digested  by  the  gastric  juice. 
The  starch,  oils  and  fats,  pass  unchanged  into  the  small 
intestine.  Here  tliey  co./ie  in  contact  with  the  mixed 
intestinal  juices,  and  are  reduced  to  a  state  fit  for  absorp- 
tion. The  juices  of  the  small  intestine  are  the  inteatiruil 
juice  proper,  or  the  fluid  secreted  by  Brunner's  glands  and 
Lieberkiihn's  follicles,  the  pancreatic  juice,  and  the  hiie. 
These  fluids,  in  contradistinction  to  the  gastric  juice,  have 
an  alkaline  reaction. 

Intestinal  Juice. — This  may  be  obtained  in  a  tolerably 
j)ure  state  by  ligating  the  duodenum  of  some  of  the  lower 
animals,  as  the  dog  or  rabbit,  just  above  the  opening  of  the 
choledcc  duct,  and  establi.shing  a  fistulous  opening  into  the 
duodenum.  It  is  small  in  quantity,  and  consists  of  the  se- 
cretion from  Brunner's  glands,  mixed  with  the  fluid  from 
the  follicles  of  Lieberkiihn,  and  some  mucus. 

Physical  Appearance  and  Properties. — It  is  a  color- 
less, viscid  fluid,  of  an  alkaline  reaction,  closely  resembling, 
in  its  physical  characters,  the  saliva  and  pancreatic  juice. 
It  possesses  the  jiroperty  of  converting  starch  into  sugar. 
The  quantity  obtained  by  experimenters  has  rarely  been 
sufficient  for  a  thorough  investigation  of  its  properties. 

Function. — It  is  supposed  to  aid  in  the  dLq-estion  of  the 
amylaceous  ])ortions  of  food.  By  its  action  starch  is 
converted  into  dextrin,  and  then  into  sugar  (glucose),  in 
which  state  it  is  soluble,  and  thus  admits  of  direct  absorp- 
tion into  the  blood-vessels,  or  the  sugar  may  be  converted 
into  lactic  acid,  and  in  this  condition  pass  into  the  circulation. 
The  presence  of  free  alkali  is  as  necessary  to  these  changes, 
as  free  acid  to  the  solution  of  the  albuminoids  by  the  gas- 
tric juice.  Boiled  starch  is  more  readily  digested  by  all 
animals  than  raw  ;  in  fact,  boiling  is  necessary  to  its  ready 
digestion. 

Pancreatic  Juice. — This  substance  is  intended  to  assist 
in  the  conversion  of  starch  into  sugar,  and  also  to  digest 
the  oily  portions  of  the  food.     It  may  be  obtained  from  the 


■( 

I 

I 

■f 

j 


tt,. 

t 

» ■ 


^1 


ti: 


14C  DIGESTION. 

dog  by  inserting  a  canula  in  the  pancreatic  duct  (major) 
through  a  fistulous  opening  in  the  abdomen.  The  ])ancreas 
in  structure,  resembles  the  salivary  glands  and  is  present  in 
all  the  vertebrate  animals.  In  the  human  subject,  the  pan- 
creatic duct  and  choledoc  duct  usually  open  into  the  duo- 
denum at  the  same  point.  In  some  of  the  vertebrata  they 
open  ai  some  distance  from  each  other,  the  pancreatic  duct 
being  usually  below  the  biliary. 

Physical  Appearance  and  Properties. — It  is  a  clear, 
colorless,  viscid  fluid,  of  an  alkaline  reaction,  somewhat 
resembling,  in  its  physical  character,  the  salivary  fluid.  It 
is  coagulated  completely  by  heat,  not  a  drop  of  fluid  being 
left.  It  is  also  coagulated  by  nitric  acid,  alcohol,  and  the 
metallic  salts.  The  precipitate  may  be  redissolved  by  the 
addition  of  an  alkali.  The  average  amount  secreted  by  the 
human  subject  in  the  course  of  twenty-four  hours,  is  about 
12  to  IG  ozs.  avoirdupois. 

Chemical  composition  of  the  pancreatic  juice  of  the  dog, 
according  to  Schmidt ;  the  following  is  the  mean  of  three 
analyses : 

Mean,  Extreme. 

Water 980.45  900.76 

P.increatine 12.71  90.44 

Sodium  and  Potassium  Chlorides 3.43  7.37 

Calcium,  Magnesium  and  Sodium  Phosphates...  .09  .53 
Soda,  Lime  and  Magnesia,  combined  with  Pan- 
creatine    .32  .90 

Traces  of  Iron 

1000.00       1000.00 

The  most  important  ingredient  is  the  organic  matter,  or 
pancreatine.  It  is  coagulated  by  heat,  niti-ic  acid  and 
alcohol.  Tt  is  also  precipitated  by  magnesium  sulphate, 
and  this  distinguishes  it  from  albumen. 

Function. — It  acts  upon  the  oily  portions  of  the  food  and 
and  fats,  partly  by  splitting  them  up  into  fatty  acids  and 
glycerine,  and  partly  by  disintegrating  them,  and  reducing 
them  to  a  state  of  complete  emulsion,  the  mixture  being 
converted  into  a  whitish,  opaque,  creamy  fluid,  which  is 
readily  absorbed.     In  disease  of  the  pancreas,  which  is  ex- 


SECRETION  Of   BILE. 


147 


ceetlingly  rare,  or  occlusion  of  the  duct,  the  patient  invaria- 
bly suffers  tA'trerne  emaciation,  and  in  some  cases  fat  ap- 
pears iu  the  fiBces.  The  pancreas  is  found  in  carnivoious 
as  well  as  herbivorous  animals,  thus  showing  that  the  pan- 
creatic secretion  is  chieHy  intended  for  the  digestion  of  fatty 
matters'  It  also  assists  in  the  conversion  of  starch  into 
sugar,  and  in  this  way  promotes  the  digestion  and  absorption 
of  aniyiaceous  food.  It  further  assists  in  the  complete 
digestion  of  albuminous  and  gelatinous  suljstances  which 
have  escaped  the  action  of  the  gastric  juice. 

Secrktion  qy  Bile. — Bile  is  secreted  by  the  cells  of  the 
liver  from  the  blood  of  the  portal  vein,  and  may  be  readily 
obtained  from  its  reservoir,  the  gall-bladdei'.  It  is  secreted 
by  the  thepatic  cells,  which  are  situated  in  the  interior  of 
the  lobules.  When  the  cells  become  filled  with  bile,  they 
break  down,  and  the  fluid  is  then  taken  up  by  the  minute 
hepatic  ducts  which  originate  in  the  interior  of  the  lobules. 
These  small  ducts,  by  frequent  successive  junctions,  form 
two  large  ducts,  each  somewhat  larger  than  a  crow-quill, 
which  emerge  at  the  transverse  fissure  of  the  liver,  one  from 
the  right  and  the  other  from  the  left  lobe.  These  two  ducts, 
together  with  the  hepatic  artery,  the  portal  vein,  nerves,  and 
lymphatics,  are  enclosed  in  a  little  areolar  tissue  called  G\is- 
soii'a  capsule,  and  about  an  inch  below  their  exit  they 
unite  to  form  the  hepatic  duct,  which  soon  unites  with  the 
cystic  duct  from  the  gall-bladder,  and  the  union  of  the  two 
constitutes  the  ductus  connnunis  choledochus.  This  i^ 
about  two  or  three  inches  long,  and  passing  down  behind 
the  first  portion  of  the  duodenum,  it  ojiens  into  the  second 
or  descending  portion,  on  its  inner  side,  a  little  below  the 
middle,  in  connection  with  the  pancreatic  duct.  The  gall- 
bladder is  situated  on  the  under  surface  of  the  right  lobe 
of  the  liver,  an<l  serves  as  a  reservoir  for  the  accumulation 
of  the  bile.  During  fasting,  the  gall-bladder  is  found  full, 
and  it  empties  itself  when  digestion  is  going  on.  The 
mechanism  is  as  follows  :  during  the  intervals  of  digestion 


1) 

.4 

1 

-.1 

i 

J 


. 


c 


•  -  • 


ff. 


146  DIGESTION. 

the  duct  below  the  junction  of  the  cystic  is  closed  by  con- 
traction of  its  muscular  fibres,  and  the  bile  being  secreted 
finds  its  way  into  the  gall-bladder,  but  on  the  introduction 
of  food  into  the  intestine,  the  bile  is  discharged  from  the 
gall-bladder  by  the  pressure  of  the  contraction  of  its  coats. 
Its  presence  is  not  essential,  for  in  many  animals  it  is  entirely 
absent,  as  in  some  of  the  fishes,  mammals,  etc.  The  hepatic 
cells  contain  more  or  less  fat  in  the  form  of  globules,  and 
this  may  be  regarded  as  part  of  their  secretion.  It  is  also 
found  to  be  most  abundant  when  fatty  matters  are  withheld 
from  the  food.  The  fat  is  formed  by  the  cells,  from  certain 
elements  of  food,  as  starch,  sugar,  etc.,  and  is  discharged 
into  the  duodenum  to  be  reabsorbed  by  the  villi,  and  carried 
to  the  lungs,  where  it  is"  decomposed  by  the  oxygen  in  the 
production  of  animal  heat. 

Physical  Appeakance  and  Properties  of  Bile. — Bile 
is  a  thick,  viscid  fiuid,  of  a  greenish  yellow  color,  a  bitter 
taste,  and  a  nauseous  smell.  Its  specific  gravity  is  about 
1020,  and  possesses  either  a  neutral  or  slightly  alkaline  re- 
action, When  agitated  in  a  test  tube  it  presents  a  peculiar 
soap-like  foam,  the  bubbles  adhering  closely  together  and 
remaining  for  a  long  time  without  breaking.  The  averafi^e 
amount  of  bile  secreted  in  twenty-four  hours  is  from  30  to 
40  ounces.  It  possesses  antiseptic  properties,  preventing 
substances  v/ith  which  it  is  mixed  from  putrefying.  When 
it  is  absent  in  the  alimentary  canal,  as  in  cases  of  complete 
biliary  obstruction,  the  fjBces  are  found  to  have  an  intoler- 
able fetor.  Bile  is  constantly  secreted  by  the  liver  but 
more  actively  from  one  to  two  and  a-half  hours  after  food 
is  taken. 

Chemical  Composition  of  Human  Bile. — Frerichs  : 

Water 859.2 

Bile  .Salts  (bilin) 91-5 

Fat 9-2 

Cholesterine 2.6 

Mucus  and  Coloring   Matter 29.8 

Salts 7-7 

ICXXJ.O 


COLORING  MATTER  OF  BILE. 


149 


A  distinguishing  feature  of  bile  is  the  absence  of  pro- 
teids  or  albuminous  substances.  The  most  important 
ingredients  are  the  coloring  matter  of  the  bile,  and  the  bile 
salts  or  hilira.  The  coloring  matter,  hilirubine,  is  a  yellow- 
ish-red cr3'stallizable  substance,  of  organic  origin.  It  does 
not  pre-exist  in  the  blood,  but  is  supposed  to  be  formed  in 
the  liver.  In  cases  of  biliary  obstruction  it  may  be 
absorbed,  and  circulating  with  the  blood,  stains  the  tissues 
and  fluids  of  the  body  of  a  greenish-yellow  or  saffron 
color,  giving  rise  to  the  state  called  jaundice.  It  is  insolu- 
ble in  water,  very  slightly  in  alcohol ;  its  best  solvent  being 
chloroform,  or  a  solution  of  soda  or  potassa.  It  becomes  green 
on  exposure  to  the  air,  and  on  the  addition  of  an  acid, 
deposits  green  flocculi  resembling  the  chlorophyl  of  plants. 
This  is  called  hillverdine,  and  a  small  quantity  is  found  in 
bile.  It  is  more  abundant  in  the  bile  of  the  herbivora. 
Two  other  colorinj+  matters  are  found  in  bile  after  remain- 
ing some  time  in  the  gall  bladder;  also  in  gall  stones,  named 
hiliprasin  and  hilifuscin. 

Cholesterine. — This  substance  may  be  removed  from 
bile  by  agitation  with  ether,  in  which  it  is  soluble.  It  is 
distinguished  from  fats,  with  which  it  is  closely  associated, 
by  not  being  saponified  by  alkalies.  It  has  also  been 
found  in  the  fluid  of  hydrocele,  ascites,  and  in  the  interior 
of  many  encysted  tumors.  It  is  a  crystallizable  substance, 
the  crystals  having  the  form  of  thin  transparent  rhom- 
boidal  plates.  Cholesteriue  is  not  formed  in  the  liver, 
but  i^  supposed  to  originate  in  the  brain  and  nerve  tissue, 
from  which  it  may  be  extracted  by  alcohol  or  ether,  and  is 
discharged  by  the  liver.  It  is  also  found  in  the  tissue  of 
the  spleen.     It  is  the  principal  constituent  of  gall  stones. 

Bile  Salts  (Bilin). — These  consist  of  sodium  glycocho- 
late  and  taurocholate ;  the  latter  predominates  in  human 
bile,  while  the  former  is  more  abundant  in  ox  bile.  The 
bilin  of  the  dog,  cat  and  other  carnivora,  consists  exclusively 
of  the  latter  .salt.     They  are  soluble  in  water  and  alcohol, 


n 


160 


DIGESTION. 


•  ♦■  *, 

\r. 

I 


V- 


■<l 


I*,  w 


but  not  in  ether.  The  taurocholate  possesses  the  property, 
when  in  solution,  of  dissolving  a  certain  quantity  of  fat. 
These  substances  may  be  obtained  as  follows  :  the  bile  is 
evaporated,  and  the  dry  residue  treated  with  alcohol  and 
filtered  ;  this  alcoholic  solution  contains  sodium  glycocho- 
late  and  taurocholate,  coloring  matter,  and  fats.  Ether  is 
now  added  until  a  precipitate  takes  place,  which  has  at 
first  a  resinous  appearance.  After  this  precipitate  has 
stood  from  twelve  to  twenty-four  hours,  it  presents,  when 
examined  by  the  microscope,  a  number  of  acicular  crystals 
of  sodium  glycocholato,  and  some  drops  or  globules  of 
sodium  taurocholate,  which  resemble  oil  globules,  except  in 
their  chemical  properties.  The  glycocholate  may  be  separated 
from  the  sodium  taurocholate  by  the  following  means: 
The  fluid  containing  alcohol  and  ether,  previously  used,  is 
poured  off,  and  the  deposit  in  the  bottom  of  the  tube  is 
dissolved  in  water.  To  this,  lead  acetate  is  added,  which 
gives  a  precipitate  of  lead  glycocholate,  leaving  sodium 
acetate  in  solution.  The  precipitate  is  filtei-ed  and  decom- 
posed by  sodium  carbonate,  reproducing  the  original 
sodium  glycocholate.  The  filtered  fiuid  which  remains, 
containing  the  sodium  taurocholate,  is  then  treated  with 
lead  subacetate,  which  precipitates  a  lead  taurocholate. 
This  is  filtered  and  decomposed  by  sodium  carbonate,  as  in 
the  former  instance.  It  crystallizes  in  slender  needles, 
much  like  the  glycocholate.  The  glycocholates  and  tauro- 
cholates  are  formed  in  the  liver,  being  produced  by  the 
hepatic  cells,  and  discharged  by  the  ducts.  They  are  not 
found  in  the  blood.  The  acids  may  be  separated  from  their 
respective  salts  by  boiling  with  dilute  sulphuric  or  hydro- 
chloric acids,  or  caustic  pot  sh,  which  also  further  splits 
up  the  glycocholic  acid  into  ylycine  and  chotic  (or  cholalic) 
acid,  and  taurocholic  into  taurine  and  cholic  acid. 

Glycogenic  Function  of  the  Livek. — The  actual  for- 
mation of  glucose,  or  grape  sugar,  in  the  liver,  was  fir.«t 
discovered  by  Claude  Bernard  in  184;8.     A  substance  called 


GLYCOGENIC  FUNCTION  OF  THE  LIVER.        151 


glycogen  is  first  formed,  and  this  is  transformed  into  sugar 
by  the  action  of  a  ferment  formed  in  the  liver.  This  sub- 
stance is  formed  by  the  liver  itself,  and  is  a  normal  con- 
stituent of  its  tissue.  Glycogen  is  identical  in  composition 
with  starch,  and  is  found  in  other  tissues  besides  the  liver, 
viz. :  in  the  muscles,  placenta,  and  embryonic  tissues.  The 
liver,  when  removed  from  the  body  of  an  animal,  and  the 
sugar  washed  completely  away,  will  be  found,  after  a  few 
hours,  to  contain  sugar  in  abundance.  Its  presence  may  be 
determined  in  the  substance  of  the  liver,  and  in  the  hepatic 
veins,  by  means  of  Tromraer's  test,  or  by  fermentation.  It 
has  also  been  found  in  the  portal  vein,  owing  to  the  reflux 
which,  in  the  absence  of  valves,  may  take  place  after 
death.  The  sugar  thus  formed  i>  carried  to  the  riglit  side 
of  the  heart,  and  thence  to  the  lungs,  where  it  is  decom- 
posed in  the  production  of  animal  heat.  Puncture  of  the 
floor  of  the  4th  ventricle,  section  of  the  cervical  sympa- 
thetic, or  inferior  ganglion,  or  irritation  of  the  central 
extremity  of  the  8th  pair,  abmjrmally  increa^'  ne  glyco- 
genic function  of  the  liver,  and  sugar  is  p.oduced  ko 
rapidly,  that  the  lungs  cannot  decompose  the  whole 
of  it,  and  therefore  it  is  thi'own  off  by  the  kidneys, 
producing  what  i  known  as  diabetes  mellitus.  Temporary 
glycosuria  may  also  be  produced  by  the  action  of  various 
substances,  as  the  inhalation  of  ether  or  chloroform,  injec- 
tion of  curare,  poisoning  by  carbonic  oxide  gas,  or  by 
injuries  to  the  brain,  and  in  the  course  of  various  diseases. 
Sugar  and  fat  are  both  formed  in  the  liver,  irrespective  of 
the  kind  or  quality  of  the  food.  Pavy  and  others  are  of 
the  opinion  that  no  sugar  exists  in  the  liver  during  life,  but 
only  occurs  after  death. 

Function  of  Bile. — During  fasting,  the  bile  is  stored  up 
in  the  gall-bladder,  but  if  the  fast  be  prolonged  beyond  a 
reasonable  time,  tlie  bile  overflows  into  the  intestine.  The 
flow  of  bile  into  the  duodenum  is  caused  by  the  presence 
of  food,  or  any  irritating  substance  upon  the   mucous  sur- 


u 


152 


DIGESTION. 


It, 

i 


<  ■    i 


face  of  the  small  intestins.  The  bile  is  poured  into  the 
duodenum,  never  below  it,  a  circumstance  not  very  proba- 
ble if  bile  were  solely  an  excrementitious  substance,  since 
it  would  have  been  quite  as  convenient  for  nature  to  have 
effected  its  discharge  into  the  hepatic  flexure  of  the  colon. 
When  the  bile  duct  is  tied,  and  this  fluid  prevented  from 
])assing  into  the  duodenum,  the  animal  becomes  greatly 
emaciated,  and  ultimately  dies  from  inanition.  There  can 
be  no  doubt,  therefore,  that  the  bile  contributes  in  some 
way  to  the  complete  digestion  and  assimilation  of  the  food. 
Bile  cannot  readily  be  detected  in  the  fteces,  and  therefore 
it  is  supposed  to  be  entirely  changed  in  its  passage  through 
the  bowels,  or  in  part  reabsorbed  with  the  chyle,  and 
thrown  back  into  the  system,  to  be  used  in  the  generation 
of  heat  by  contact  with  oxygen  in  the  lungs. 

Bile  is  both  an  excrementitious  and  digestive  substance. 
That  it  is  excrementitious  is  evidenced  in  the  com))aratively 
large  size  of  the  liver  and  the  active  formation  of  bile  in 
the  fwtus,  and  the  presence  of  meconium  (biliary  matter) 
as  faeces  in  the  intestines.  The  ffieces  of  the  adult  also  con- 
tain the  coloring  matters,  some  fatty  matter,  and  a  small 
quantity  of  bilin.  Through  the  bile  is  eliminated  carbon, 
hydrogen,  and  other  elements  from  the  blood,  which  if 
allowed  to  accumulate,  would  render  it  impure.  Dr.  Flint 
regards  the  excretion  of  cholcsterine,  which  is  changed  into 
stercorine  in  the  bowels,  as  an  important  function  of  the 
liver.  As  a  digestive  it  assists  in  emulsifying  the  fatty 
matters,  and  by  reason  of  its  alkalinity  favors  their  absorp- 
tion. The  liver  also  performs  an  important  ofiice  in  remov- 
ing substances  which  have  been  taken  up  by  the  portal 
vein  during  digestion,  which  would  be  injurious  if  allowed 
to  enter  the  circulation.  We  may  therefore  conclude  as  fol- 
lows:  that  the  liver  secretes  a  complex  fluid,  the  "bile," 
which  is  poured  into  the  duodenum.  Its  coloring  matters 
and  some  of  the  fatty  matter  and  salts,  are  carried  off"  in 
the  faeces  forming  the  natural  purgative  of  the  body,  and 


TESTS  FOR  BILE. 


153 


by  virtue  of  its  antiseptic  properties,  preventing  decomposi- 
tion of  the  frecal  matters.  Its  fat  and  bilin  are  in  great  part 
reabsorbed.  It  also  assists  in  the  complete  digestion  of  those 
parts  of  the  food  which  have  escaped  digestion,  as  starch 
and  fatty  matters.  It  forms  sugar  and  fat  in  the  circula- 
tion, independently  of  the  substances  in  the  food.  It  elimi- 
nates carbonaceous  matters ;  some  directly,  as  the  coloring 
matter,  small  quantities  of  fat  and  bilin  ;  others  indirectly, 
as  fat.  sugar,  and  bilin,  which  pass  to  the  lungs,  and  are 
converted  into  carbonic  acid  and  water  by  the  oxygen. 

Tests  for  Bile.  —  When  nitric  or  nitroso-nitric  acid 
(Gmelin's  test)  is  added  to  a  mixture  containing  bile,  and 
shaken,  a  play  of  colors  is  produced,  changing  from  green 
through  various  tints  to  red.  This  does  not  indicate  the 
presence  of  biliary  substances  proper,  but  only  the  coloring 
matters. 

Pettenkofer's  Test. — This  is  the  best  test  for  the  detec- 
tion of  bilin.  A  watery  solution  of  the  bile  is  mixed  with 
a  drop  or  two  of  a  solution  of  cane  sugar  ;  sulphuric  acid  is 
then  added  to  the  extent  of  two-thirds  of  the  liquid,  and  a 
red,  violet,  and  purple  color  are  produced  in  succession. 
The  reaction  consists  in  the  liberation  of  cholic  acid  from 
the  glyco-cholic  or  tauro-cholic  acid  of  the  biliary  salts.  The 
sugar  must  be  used  in  small  quantities,  for  when  added  in 
excess,  it  is  liable  to  be  acted  on  and  discolored  by  the  sul- 
phuric acid.  The  solution  of  sugar  should  be  about  one 
part  sugar  to  four  parts  water.  Foreign  matters,  not  of  a 
biliary  nature,  such  as  oleine,  ethereal  oil,  amyl-alcohol,  albu- 
minous matters,  and  the  salts  of  morphine  and  codeine,  may 
produce  a  similar  red  or  violet  color.  This  may  be  over- 
come, however,  by  first  extracting  the  suspected  matters 
with  alcohol,  precipitating  with  ether,  and  dissolving  the 
precipitate  with  water,  before  applying  the  test. 

The  specti'U7)i  of  Pettenkofer's  test  presents  characters 
which  may  distinguish  it  from  the  reactions  produced  by 
other  organic  substances.     If  some  of  the  colored  fluid  ta 


'1 
f 

M 

I 

It 

) 


154- 


DIGESTION, 


I  lb:  -i. 

ri. 


if 

*■  ,-■ 

r\ 

k.  •;- 
»..    , 

I.   '•, 


which  the  cane  sugar  and  sulphuric  acid  have  been  added 
be  placed  before  the  slit  of  the  spectroscope,  its  spectrum 
shows  a  broad,  dark  absorption  band  at  E*,  and  extending 
to  midway  between  d  and  E.  the  central  part  of  the  band 
being  darker  than  the  edges.  When  an  alcoholic  solution 
of  Pettenkofer's  test  is  examined  as  above,  two  absorption 
bands  are  seen ;  one  at  E,  identical  with  the  one  seen  in  the 
watery  solution ;  and  the  other  at  F,  narrower  and  fainter 
than  the  one  at  E,  (Fig.  ho). 


Yv'.  .'•,.'). 


Spectrum  of  Pettenkofer's  test  with  the  biliary  saits  in  alcoholic  solution. 

Bile  if^  also  dichroic,  or  presents  two  different  colors 
when  examined  by  transmitted  light,  according  to  the 
thickness  or  thinne.ss  of  the  stratum  under  examination 
It  is  alao  Jluorescent,  or  faintly  luminous  with  a  color  of  its 
own,  especially  when  examined  by  the  more  refrangible 
rays  of  the  solar  spectrum. 

Summary. — The  digestion  of  the  food  is  not  a  simple 
operation,  but  consists  of  several  different  proces.ses,  which 
occur  successively  in  different  portions  of  the  alimentary 
canal.  The  food  is  first  subjected  to  the  physical  opera- 
tion of  mastication  and  insalivation  in  the  mouth.  It  then 
passes  into  the  stomach,  where  it  meets  with  the  gastric 
juice,  which  converts  it  into  a  pulpy  mass — the  chyme. 
Here  certain  soluble  elements  of  the  food,  as  water,  wine, 

*  The  solar  spectrum  is  crossed  by  vertical  lines  known  as  Frauenhofer's 
lines,  and  designated  A,  n,  c,  i),  E,  K,  G  and  ii.  The  situation  of  an 
absorption  band  is  indicated  by  reference  to  one  or  more  of  these  letters. 


LARGE  INTESTINE, 


155 


tea,  saline  matters,  sugar,  and  a  certain  quantity  of  albumi- 
nose  are  absorbed  by  the  veins  and  lymphatic  vessels  of  the 
stomach.  The  food  then  passes  into  the  duodenum,  or  small 
intestine,  carrying  with  it  the  gastric  juice,  where  it  meets 
with  the  intestinal  juices,  pancreatic  juice  and  bile.  The 
albuminous  matters  which  were  not  wholly  digested  in  the 
stomach  are  now  dissolved ;  starchy  matters  are  converted 
into  dextrine  and  sugar,  the  oils  and  fats  are  emulsified,  and 
the  fluid  is  converted  into  chyle.  This  is  taken  up  by  the 
lacteals  or  blood-vessels  in  the  process  of  absorption,  and 
the  coarser  portions  of  the  food,  or  excrementitious  matters 
of  the  body,  are  carried  off"  by  the  large  intestine. 

Large  Intestine. — Its  office  is  mainly  confined  to  the 
separation  and  discharge  of  the  freces.  The  mucous  mem- 
brane of  the  large  intestine  is  destitute  of  villi,  and  val- 
vula3  conniventes.  Beneath  the  mucous  membrane  are  found 
a  few  nonstriated  muscular  fibre  cells  (muscularis  mucosie.) 
The  glands  are  of  two  kinds  tubular  or  glands  of  Lieberkuhn, 
and  lenticular  glands.  The  former  are  larger  than  those  in 
the  small  intestine,  and  the  latter  closeiy  resemble  the  glan- 
dula3  solitarije,  and  are  most  numerous  in  the  csecum  and 
vermiform  appendix. 

The  ileo-ciecal  valve  is  situated  at  the  junction  of  the 
ileum  with  the  crecum,  and  prevents  reflux  of  the  contents 
of  the  latter.  It  consists  of  two  semilunar  folds  of  mucous 
membrane,  each  of  which  contains  vessels,  nerves  and  lym- 
phatics, together  with  some  of  the  muscular  fibres  of  the  in- 
testine. By  dividing  the  longitudinal  muscular  fibres  and 
peritoneum  at  the  margin  of  the  valves,  they  may  be  made 
to  disappear,  just  in  the  same  way  as. the  sacculi  of  the  large 
intestine  can  be  obliterated,  by  a  similar  operation.  The 
surface  of  the  valve  next  the  ileum  is  covered  with  villi, 
but  they  are  entirely  absent  on  the  surface  next  the 
caecum. 

It  is  supposed  by  some  that  a  certain  amout  of  digestion 

takes  place  in  the  caecum.     In  some  animals  it  is  very  large, 
8 


'1 
f 

M 
A 

! 

i 


15G 


DIGESTION. 


'It: 

«  . 


■'!  I  il 


I;" 


and  would  seem,  without  doubt,  to  exercise  some  special 
function  in  the  complete  solution  of  the  food.  But  in  man  it 
is  quite  rudimentary,  and  has  very  little  action  upon  the 
feces  in  their  passage  through.  No  material  change  takes 
place  in  the  fseces  as  they  pass  through  the  intestine,  ex- 
cepting that  they  become  drier  the  longer  they  remain  in 
the  bowel,  owing  to  the  absorption  which  takes  place.  Nu- 
tritive enemata  may  also  "be  absorbed  by  the  largo  intestine. 
The  fjcces  are  urged  onwards  to  the  rectum  by  the  vermic- 
ular action  of  the  bowel,  where  they  accumulate,  and  are 
prevented  from  escaping  by  the  contraction  of  the  sphincter. 
The  presence  of  the  accumulated  frecal  matter  in  the  rectum, 
causes  a  sensation  demanding  its  discharge  or  defiecation. 

DEFECATION. 

This  is  the  expulsion  of  the  freces  from  the  rectum,  and  it 
is  effected  by  the  contraction  of  the  muscular  fibres  of  the 
rectum,  assisted  by  the  contraction  of  the  abdominal  muscles 
and  diaphragm,  which  diminish  the  size  of  the  abdominal 
cavity,  compress  the  intestines,  and  thus  force  onwards  the 
foecal  matter  towards  the  anus.  This  force  is  at  the  same 
time  quite  sufficient  to  overcome  the  passive  contraction  oi 
the  sphincter.  If  the  rectum  be  over-distended  by  fsecal 
matter,  its  contractility  will  be  diminished,  and  immense 
accumulations  may  take  place.  This  is  apt  to  occur  in  aged 
persons,  and  the  faecal  matter  may  lequire  to  be  scooped 
out.  On  the  other  hand,  when  the  fseces  do  not  accumulate 
in  sufficient  quantity  to  distend  the  rectum,  the  act  of  de- 
fnecation  may  be  attended  with  difficulty,  and  the  straining- 
may  cause  prolapsus  ani.  Under  such  circumstances  ene- 
mata are  of  great  service,  by  distending  the  bowel  and 
stimulating  it  to  proper  action. 

The  quantity  of  faeces  depends  on  the  nature  of  the  food 
and  the  state  of  the  system.  Vegetable  food  produces  a 
greater  amount  of  faeces  than  animal,  because  it  contains 
much  that  is  incapable  of  reduction  in  the  stomach  and  duo- 


SALTS  OP  FAECES.  157 

donum.  Tlie  quantity  passed  daily  in  liealtli  is  from  four 
to  eight  ounces  ;  so  that  if  we  assume  thirty- five  ounces  to 
be  the  average  quantity  of  food  per  day,  it  may  be  inferred 
tliat  about  thirty  ounces  are  appropriated  for  the  support 
of  the  body. 

Analysis  of  Faeces — 

Water 73.3 

Excrctine,  .stercorine,  salts  and  fatty  acids 

Insoluljle  residue  of  food,  coloriiiy  matter  and  other  ingre- 
dients of  bile,  mucus  anil  epithelium 26. 7 

Exckp:tine  was  discovered  by  Marcet  and  is  associated 
with  excretolic  acid.  It  is  a  crystal lizable  substance,  in- 
soluble in  water,  but  soluble  in  ether  and  hot  alcohol,  and 
is  slightly  alkaline.  The  crystals  are  in  the  Ibrm  of  four- 
sided  prismatic  needles.     It  fuses  at  lOVY. 

Stercorine  was  discovered  by  Prof.  Flint,  Jr.  It  has 
the  same  crystalline  form  as  excrctine,  is  also  soluble  in 
ether  and  boiling  alcohol,  but  fuses  at  a  lower  temperature. 
It  is  supposed  to  be  formed  from  cholesterine. 

Salts  of  Faeces. — These  consist  chiefly  of  calcium  and 
magnesium  phosphates,  iron,  soda,  lime  and  silica. 

The  peculiar  odor  of  the  faeces  is  supposed  to  be  caused  by 
the  secretion  of  the  glands.  Certain  gases  are  also  generated 
in  the  bowels.  They  consist  of  carbonic  acid,  hydrogen, 
carburetted  hydrogen,  sulphuretted  hydrogen  and  nitrogen. 
They  would  seem  to  favor  the  passage  of  the  fsecal  matter 
by  their  distension  of  the  bowel.  In  some  diseases,  as  hys- 
teria, puerperal  fever,  inflammation  of  the  bowels,  etc.,  large 
quantities  of  gas  are  accumulated,  producing  iympanites  or 
meteorisru.  The  natural  color  of  the  faeces  is  yellow,  but  in 
biliary  obstruction  they  become  clay-colored  and  ofi'ensive. 
Again,  when  the  bile  -is  vitiated,  or  secreted  in  large  quan- 
tity, they  vary  from  green  to  dark  brown. 


'1 
f 

% 

It 

1 
f 

J 


158 


ABSORPTION, 


CHAPTER  VI. 


(11 


ABSORPTION. 

All  the  tissues  of  the  body  are  more  or  less  porous,  and 
<5apable  of  absorbiiifj  fluids  brought  into  contact  with  them ; 
but  the  special  absorbents  are  the  blood-vessels,  villi  and 
lacteah,  lymphatic  vessels  and  glands,  and  'prohahhj  the 
glandula?  solitarim. 

Blood-Vessels. — The  structure  and  general  function  of 
the  blood-vessels  will  be  described  in  the  chapter  on  cir- 
•culation. 

Villi  and  Lacteals. — The  structure  of  the  villi  has 
been  already  described  among  the  appendages  of  the  mu- 
cous membrane,  (page  111,  Fig.  50.)  In  consequence  of 
their  number  and  form,  they  increase 
.greatly  the  secreting  surface  of  the 
intestine.  They  hang  out  in  the  nutri- 
tious semi-fluid  mass  contained  in  the 
intestinal  cavity,  like  the  roots  of  a  tree 
in  its  soil,  and  rapidly  imbibe  the  soluble 
portions  of  the  food. 

The  lacteals  commence  near  the  apex 
•of  each  villus  either  by  a  blind  extremity, 
or  minute  plexus,  the  precise  manner  is 
not  known.  In  structure  they  resemble 
the  capillaries, having  an  outer  structure- 
less or  finely  fibrillated  membrane ;  and 
an  inner  endothelial  lining.  They  form 
a  network  with  close  meshes  in  the  sub- 
mucous areolar  tissue,  and  then  pass 
between  the  layers  of  the  mesentery 
towards  its  root, anastomosing  freely  with 
each  other,  and  traversing  the  mesenteric 
glands  in  their  way  to  the  right  side  of  the  aorta,  opposite 


An  intestinal  villus ;  (a) 
columnar  epithelium  ;  (b) 
capillaries  ;  (c)  nonstriated 
muscular  fibre  cells;  (d) 
lacteal. 


LYMPHATIC  VESSELS  AND  GLAI^DS. 


15t) 


the  second  lumbar  vertebra,  where  they  empty  them- 
selves, together  with  the  lymphatics  from  the  lower 
extremities  into  the  receptaculum  ehyli,  or  commencement 
of  the  thoracic  duct.  The  thoracic  duct,  which  is  continued 
upwards.lies  between  the  aorta  and  vena  azygos  major  in  the 
thorax ;  it  then  passes  behind  the  arch  of  the  aorta,  and 
empties  itself  into  the  upper  part  of  the  loft  subclavian  vein, 
close  to  the  internal  jugular,  its  orifice  being  guarded  by 
two  valves.  The  lacteals,  are,  however,  not  a  si)ecial  system 
of  vessels  by  themselves,  but  may  be  considered  as  a  part 
of  the  general  lymphatic  system.  Their  function  is  to  ab- 
sorb the  chyle. 

Lymphatic  Vessels  and  Glands. — These  constitute  the 
chief  system  of  absorbents  of  the  body.  They  are  found  in  , 
nearly  every  part  of  the  body,  except  the  substance  of  the 
brain  and  spinal  cord,  eye-ball,  cartilage,  tendons,  mem- 
branes of  the  ovum,  placenta,  funis,  hair,  nails  and  cuticle. 
They  commence  either  in  a  closely  meshed  network,  or  in 
irregular  lacunar  spaces  among  the  tissues  termed  the 
lym'ph  canalicular  system.  The  latter  form  a  connected  sys- 
tem of  very  irregular  branched  spaces  beneath  serous  mem- 
branes, as  the  pleura  and  peritoneum.  Recklinghausen  has 
shown  that  the  serous  membranes  are  studded  with  stomata 
which  are  the  openings  of  short  vertical  canals  which  com- 
municate with  the  lymph  canalicular  system.  The  serous 
cavities  are  therefore  looked  upon  as  large  lymph  sinuses, 
or  expansions  of  the  lymph-canalicular  system,  (page 
101.)  There  are  two  sets  of  lymphatics,  the  superjicial  and 
deep ;  the  former  are  situated  in  the  supei-ficial  fascia,  and 
the  latter  accompany  the  deep  blood-vessels.  Those  of  the 
lower  extremeties  empty  into  the  receptaculum  chyli,  which 
is  continued  upwards  through  the  thoracic  duct,  to  the  left 
subclavian  vein,  and  those  of  the  upper  extremities,  head 
and  neck,  empty  by  a  short  trunk  into  the  subclavian  vein 
of  the  right  side. 


'I 


IfiO 


AnsORPTION,. 


C 

V. 

•  -"  ■( 

»■»'  -• 


•  » 


Structure. — The  lymphatic  vessels  are  remarkable  for 
the  transparoncy  of  their  walls.  The  larger  vessels  like  the 
arteries  and  veins  are  composed  of  three  coats.  1st,  an 
inner  ej^ithelial,  (or  endothelial)  and  elastic  ;  2nd,  a  middle, 
muscular  and  elastic,  disposed  transversely  ;  and  3rd,  an  ex- 
■  ternal,  areolar  and  elastic  coat.  They  are  also  provided 
with  valves  like  the  veins,  arranged  in  pairs,  which  pievent 
regurgitation,  and  assist  in  the  onward  flow  of  the  fluid 
which  the  vessels  contain.  The  valves  are  more  numerous 
in  the  lymphatics  than  in  the  veins,  and  the  walls  of  the 
vessels  are  thinner  and  more  transparent.  Then^  is  no  di- 
rect communication  between  tho  lymph-capillaries  and 
blood-capillaries,  as  was  formerly  supi)osed.  The  lymphatic 
vessels  may  be  readily  brought  into  view  by  injecting  the  n 
with  mercury.  The  vessels,  in  their  course,  ])ass  through 
certain  glandular  bodies — the  "  lymphatic  "  or  "  absoi'beut  " 


nrlauds. 


FiR.  r>7. 


LYMPirATio  Glands. — The  lym- 
phatic glands,  among  which  may  bo 
included  the  mesaiicric  glands,  con- 
sistof  an  external  layer  of  connect- 
ive tissue, and  u'landular  tissue  within. 
From  the  innner  surface  of  the  exter- 
nal layer  thin  septa  or  trabecuhe  are 
given  ott',  which  penetrate  the  interior 
of  the  gland  in  eveiy  direction,  and 
unite  with  each  other  at  various 
points,  so  that  the  substance  of  the 
gland  isdividedinto  numerous  spaces 

.\  IvniplmtiL'  ylaiui   and  vessels  ,         ,.         i   •    i  -       ,  >  .t 

fiuoii  with  inemiry;  1,  iifforcnt  or  (Uveoli,  wliich  communicatc  With 

vessels  ;  i.  efferent  vessels ;  (b)  a  i         ■  i  mi  i  i        •       /» 

lyniphatie  vessel  showiiijf   the  cach  othcr.     .1  lie  uctworK   IS  hncr 

valves  ;  (e)  Ivnipli  eornuseles,  one    •       ,,  ,       ,  7     ji  ,1 

granular  anil  three  treated  with  111  the  Central  Or  DiednlUiry,  tliaii  in 

acetic  acid  showinj;  the  cell  wall       ,  ■•       j  •'  mi 

and  nucleus,  also  some  fine  Rran-    the    CO'i    ICClL    portlOn.        1  lieSC    SpaCBS 

iiles  and  oil  globules,  (Mascagni)  /.ii     1       •  L^  i  i        i>       a-j" 

X  4(X).  are  nlled  with  a  network  ot  retiform 

or  adenoid  tissue  (p.  71),  the  interstices  of   which  are  filled 
with  lymph  corj)uscles,  and  arc  penetrated  like  the  solitary 


LYMPH  AND  CHYLE. 


161 


trlands  by  a  network  of  capillaries.  The  lymph  corpuHclen 
chiefly  occupy  the  central  part  of  the  alveoli,  forniintj;  with 
the  retiform  tissue,  nodules  and  cords,  leavirijr  a  space  in  the 
outer  portion  for  the  circulation  of  the  lymph,  called  the 
bjimpJi-pat}!,.  Each  lymphatic  vessel,  as  it  enters  the  gland, 
divides  into  a  number  of  small  branches,  called  the  vasa 
affereni'm  which  communicate  with  the  lymph-paths  ;  other 
similar  twigs  form  the  vasa  ejfercntia,  which  leave  the  gland 
in  the  opposite  diiection.  The  lyniphatic  glands  an;  arranged 
in  chains,  in  various  parts  of  tlie  body,  as  in  the  groin 
parallel  to  Poupart's  ligament,  and  along  the  posterior  border 
of  the  sterno-cleido-mastoid  nmscle,  etc.  They  vary  in  size 
from  a  millet  seed  to  a  pea.  The  vessels  and  glands  con- 
tain a  fluid  termed  lymph. 

Lymi'H  and  Chyle — Lymjth  is  a  colorless,  or  pale-yellow, 
transpaient  fhiid,  of  a  slightly  alkaline  reaction,  and  a  saline 
taste.  It  contains  nucleated  corpuscles,  resembling  those 
found  in  chyle,  but  less  numerous,  which  are  supposed 
ultimately  to  form  blood  coi'puscles.  It  is  spontanec  'isly 
coagulable  when  removed  from  the  vessels,  owing  to  the 
})resence  of  fibrin,  which  is  more  abundant  in  the  large 
than  in  the  small  vessels.  The  albumen  is  smaller  in  ([uan- 
tity  than  in  chyle,  and  there  is  scarcely  any  fatty  matter. 
The  ingredients  of  lymi»h  are  chiefly  the  i)roducts  of  the 
exudation  from  the"cai)illaries,  and  the  waste  of  the  tissues. 
It  is  identical  in  great  part  with  the  liquor  sanguinis  of  the 
blood. 

Chyle  is  a  whitish,  opalescent  fluid  re- 
sembling milk,  of  an  alkaline  reaction,  and 
contains  numerous  fat  globules  i'rom  i„, ',,,(. 
to  sohoo  of  an  inch  (1.25  to  .8  mmm)  in  dia- 
meter, V  hich  constitute  the  molecular  bane 
of  chyle.     The  fat  globules  are  soluble  in 

6ther.  Fat  KlobuloM  of  chyle. 

As  the  chyle  passes  onwards  towards  the  ihoracic  duct,  it 
becomes  more  fully  elaborated,  the  quantityof  molec  lies  or  oil 


t 

It 
I 


in:* 

If: 

1!. 

I'-  ■ 

I  ■  . 


1^ 

I! 


162 


ABSORPTION. 


globules  diminish, nucleated  cells  ^/^o  to  -j^yVn  of  au  inch,  (9.6 
to  8.3  mmm)  in  diameter,  called  chyle  corpuscles,  are  formed 
in  it, and  by  the  development  of  fibrin,it  acquires  the  property 
of  coagulating  spontaneously.     The^higher  it  ascends  in  the 

thoracic  duct,  the  more  fully  is  it 
elaborated,  the  chyle  corpuscles 
are  more  numerous,  and  advanced 
towards  their  development  into 
red  blood  corpuscles,  and  the  clot 
coagulates  more  firmly. 

These  two  fluids — lymph  and 
chyle — are  nearly  similar,  as  will 
be  seen  from  the  following  table 
which  is  the  result  of  an  analysis 
of  the  lymph  and  chyle  of  a 
donkey  by  Owen  Rees. 


Molecular  base  and  coriHiscles  of 
chyle  from  the  receptaculura  chyli  of 
a  man. 


Chemical  Constituents. — 

Lymph.  Chyle. 

Water 96. 54  90.24 

Albumen 1.20  3.52 

Fibrin o.  12  0.37 

Fat A  trace.  3.60 

Extractive 1.56  1.56 

Salt 0.58  0.71 

100.00  100.00 

MECHANISM   OF    ABSORPTION. 

Imbibition  or  osmosis  is  a^ physico-chemical  process,  and 
occurs  in  inorganic  as  well  as  in  dead  or  living  organic 
bodies.  It  depends  on  the  force  of  adhesion  between  a  fluid 
and  a  porous  solid,  by  which  the  fluid  is  drawn  into  the  in- 
terstitial passages  of  the  solid.  The  fluid  chiefly  concerned 
in  this  process  is  water,  and  the  various  other  substances 
which  are  taken  up  in  a  state  of  solution,  as  fibrin,  albumen, 
salts,  gases,  etc.  The  process  of  osmosis  in  the  living  body 
however,  is  regulated  and  controlled  by  the  agency  of  cells, 
which  have  the  power  of  choosing  and  refusing  from  the 
materials  brouffht  into  contact  or  relation  with  them. 


MECHANISM  OF  ABSORPTION. 


163 


The  quality  of  the  fluid  influences  absorption.     If  water 
be  brought  in  contact  with  the  surface  of  the  body,  or  taken 
into  the  stomach,  it  is  readily  absorbed,  especially  in  the 
latter  case,  because  it  is  brought  nearer  the  blood-vessels ; 
or  if  a  quantity  of  warm- water  is  injected  into  the  colon,  it 
is  rapidly  absorbed  and  excreted  by  the  kidneys.     But  if  the 
water  contain  a  quantity  of  sodium  chloride,  or  any  salt  in 
solution,  it  will  be  absorbed  more  slowly,  while  if  a  saturated 
solution  be  used,  the  fluid  portion  of  the  blood  will  pass  out 
of  the   blood-vessels  to  mingle  with  it.     When  the   fluid 
passes  from  without  inwards  the  process  is  termed  endos- 
mosis ;  when  f i  om  within  outwards,  exosmosis.    The  term  os- 
mose or  osmosis  refers  simply  to  the  passage  of  a  fluid  in 
either  direction,  and  is  much  more  convenient.     This  pro- 
perty of  endosraosis  and  exosmosis  may  be  demonstrated  by 
placing  a  membranous  partition  through  a  vessel  of  earthen- 
ware and  placing  pure  water  on  one  side,  and  a  solution  of 
salt  and  water  on  the  other.     It  will  be  found  that  the  water 
will  pass  more  rapidly  through  the  membrane  to  the  side 
containing  the  salt  and  water,  but  that  after  a  time  both 
sides  will  be  equally  impregnated  with  salt.     In  this  case 
the  passage  of  the  water  to  the  salt  is  called  "  endosmosis," 
and  the  more  scanty  passage  of  salt  to  the  water  "  exos- 
mosis.''    The  instrument  used  for  measuring  the  rapidity  of 
osmosis,   is   called   an   endosmometer.     A   very  good   one 
may  be  made  from  a  common  glass  funnel  by  tying  a  piece 
of  bladder  over  the  lower  end,  and  fixing  a  glass  tube,  open 
at  both  ends,  in  an  upright  position  within  the  funnel.     The 
instrii  inent  is  next  filled  with  a  solution  of  salt  or  sugar,  and 
put  in  a  vessel  containing  pure  water.     The  water  will  then 
pass  through  the  membrane  at  the  bottom  of  the  funnel  into 
the  solution  by  osmosis,  and  cause  the  fluid  to  ascend  in  the 
tube,  which  may  have  been  previously  marked,  or  graduated, 
by  a  common  file.     The  height  to  which  the  fluid  rises  in  a 
given  time,  is  a  measure  of  the  rapidity  of  endosmosis  over 
exosmosis.  Substances  are  divided  into  two  classes  according 


1 

.4 
I 

I 

if 

i 


II. 

I'*  - 

a  ■ 


ii 


164 


ABSORPTION. 


to  their  facility  of  osmosis ;  those  which  pass  through 
readily,  and  which  are  usually  cr3'stallizable,  are  called  c?'2/s- 
talloids,  and  those  which  pass  with  difficulty,  colloids.  The 
colloids  are  also  distinguished  from  crystalloids  by  their  in- 
ertness as  f  3ids  or  bases. 

The  cha .  acter  of  the  membrane  and  its  affinity  for  the 
fluids  influence  absorption.  If  a  piece  of  bladder  be  placed 
between  alcohol  and  water,  the  current  is  from  the  water  to 
the  alcohol,  on  account  of  the  greater  affinity  of  the  water 
for  this  membrane ;  but  if  a  membrane  of  India  rubber 
be  used,  the  current  is  reversed.  It  is  necessary  that  the 
membrane  should  be  fresh.  If  it  be  in  a  state  of  decay,  or 
if  it  has  been  dried,  it  will  not  produce  the  desired  effect. 
The  position  of  the  membrane  causes  a  variation.  In  some 
instances,  endosmosis  is  more  rapid  when  the  mucous  sur- 
face is  in  contact  with  the  denser  solution.  In  other  cases, 
it  is  exactly  the  reverse.  The  density  or  laxity,  and  the 
thickness  or  thinness  of  the  membrane,  also  affect  the  result 
for  obvious  reasons. 

Pressure  influences  absorption.  It  promotes  the  trans- 
mission of  a  fluid  through  a  membrane,  and  the  rapidity 
of  osmosis  will  depend,  "  cccteris  imribus"  on  the  de- 
gree of  pressure  emjiloyed.  Since  this  promotes  the  flow 
in  one  direction,  it  also  tends  to  retard  the  passage  of  fluids 
in  the  opposite  direction ;  for  example,  when  the  blood-ves- 
sels are  distended  with  blood,  as  in  plethora  or  inflam- 
mation, fluids  enter  with  difficulty  from  without,  while  if 
the  tension  be  removed  by  venesection,  absorption  takes 
place  quite  readily. 

Motion  of  the  fluid  in  the  vessels  influences  absorption. 
The  motion  of  the  fluid  within  the  vessels  promotes  absorp- 
tion, by  diminishing  the  pressure  outwards  on  the  walls 
and  allowing  the  external  pressure  to  predominate,  and  also 
by  moving  the  particles  onwards,  to  make  room  for  those 
which  are  being  absorbed. 


ABSORPTION  BY  THE  LACTEALS. 


165 


Absorption  by  the  Villi  and  Lacteals. — During  the 
intervals  of  digestion,  the  lacteals  contain  a  colorless  trans- 
parent substance,  similar  to  that  which  is  obtained  in  other 
parts  of  the  lymphatic  system.  If  the  food  consists  only  of 
starchy  and  albuminous  substances,  very  little  change  is 
noticed  in  the  character  of  their  contents.  But  if  fat  has 
been  taken,  the  lacteals  become  filled  with  a  white  chyle  or 
"  molecular  base,"  consisting  of  minute  fat  globules  and  a 
small  quantity  of  fibrin,  albumen,  (or  albuminose),  etc.  The 
presence  of  chyle  in  the  lacteals  is  therefore  not  constant, 
but  occurs  during  the  process  of  digestion,  or  as  soon  as  the 
fatty  matters  of  the  food  have  been  disintegrated  and  emul- 
sified by  the  intestinal  fluids.  The  absorption  of  fat  from 
the  intestine  is  not  performed  exclusively  by  the  lacteals 
but  some  of  it  is  taken  up  by  the  blood-vessels,  for  it  has 
been  found  by  Bernard  in  the  blood  of  the  mesenteric  veins 
of  the  carnivora  during  digestion.  It  has  also  been  found 
in  the  blood  of  the  portal  vein.  Fat  being  a  non-osmotic 
substance,  especially  when  the  membrane  is  moist,  a  diffi- 
culty has  been  experienced  in  accounting  for  its  absorption. 
It  has  been  found,  however,  that  the  presence  of  an  alkaline 
fluid,  as  bile,  mixed  with  emulsified  fat,  will  facilitate  the 
process  of  osmosis,  and  secure  the  complete  absorption  of 
the  fatty  matter. 

The  chyle  and  other  fluids  are  absorbed  by  the  pro^  ss  of 
osmosis,  which  is  regulated  and  controlled  by  the  agency  of 
cells.  The  epithelial  cells  covering  the  free  surface  of  the 
villi  are  the  first  active  agents  in  this  absorption,  for  during 
the  process  of  digestion  they  are  found  filled  with  chyle. 
They  break  down,  and  the  fluid  passes  through  the  base- 
ment membrane  by  osmosis  (endosmosis)  into  the  adenoid 
tissue  of  the  villi  being  regulated  and  controlled  by  the 
lymphoid  cells  which  are  found  in  its  meshes,  and  in  con- 
tact with  the  lacteals.  The  chyle  then  comes  in  direct  con- 
tact with  the  lacteals  through  the  coats  of  which  it  again 
passes  by  osmosis,  the  process  being  determined  by  the  cells 


I 

.4 

} 
(I 

1 


1C6 


ABSORPTION. 


«; 


t 


l» 


ti 
•  r 


whicli  lino  the  interior  of  the  lacteals.  The  fluid  then 
passes  to  the  receptacuhini  cliyli,  and  thence  tlnough  the 
thoracic  duct  to  the  left  suhclavian  vein.  Its  onward  flow 
is  facilitated  by  the  contractile  tissue,  which  is  found  in  the 
tissue  surrounding  the  lacteals  and  in  the  tlioracic  duct,  and 
it  is  prevented  from  regurgitating  by  the  valves  which  are 
found  in  the  latter  vessel. 

AnsoiiPTioN  iJY  THK  Blood-Vessels. — That  the  blood- 
vessels absorb,  has  been  proved  by  the  ex])erinionts  of 
Magendie  and  Panizza.  The  latter  observer  opened  the  ab- 
domen of  a  hoi'se,  and  drew  out  a  portion  of  the  small  in- 
testine, eight  or  nine  inches  in  length,  which  ho  enclosed 
between  two  ligatures.  He  then  ligated  the  mesenteric 
vein,  and  made  an  opening  behind  the  ligature,  in  order  to 
allow  the  blood  brought  by  the  artery  to  pass  out.  An 
opening  was  also  made  in  the  intestine,  through  which  was 
introduced  some  hydrocyanic  acid,  and  almost  immediately 
afterwards,  it  was  detected  in  the  blood  which  flowed  from  the 
ope'^ing  in  the  vein.  The  above  experiment  was  varied  by 
simply  compressing  the  vein,  and  introducing  hydrocyanic 
acid  in  the  intestine.  In  this  case  no  effect  was  produced 
on  the  animal  while  compression  was  maintained,  but  as 
soon  as  the  pressure  was  removed,  symptoms  of  poist)ning 
by  hydrocyanic  acid  showed  themselves.  The  rapidity  with 
which  the  blood-vessels  absorb  certain  substances  may  be 
seen  in  the  administration  of  alcoholic  and  other  soluble  sub- 
stances by  the  stomach,  and  also  the  hypodermic  injection 
of  morphine  and  other  alkaloids.  The  blood-vessels  not 
only  perform  an  active  part  in  the  general  absorption  of 
fluids  in  various  parts  of  the  body,  but  are  also  specially  en- 
gaged in  the  absorption  of  the  alimentary  fluids  of  the  in- 
testine. The  albuminous  and  starchy  portions  (and  even 
fatty  matters)  of  the  food  are  absorbed  by  them  from  the 
mucous  surface  of  the  stomach  and  small  intestine,  in  the 
form  of  albuminose  and  glucose.  The  substances  taken  up 
by  the  veins  are  thence  conveyed  by  the  portal  system  to  the 


ABSORPTION  BY  THE  LYMPHATICS. 


167 


liver,  where  some  of  them  arc  acted  upon  by  that  organ  in 
the  production  of  bile,  sugar,  fat,  etc.,  some  of  which  are 
carried  back  iuto  the  alimentary  system,  and  otheis  are 
thrown  into  the  general  circulation.  In  the  process  of  ab- 
sorption, the  substances  pass  through  the  basement  mem- 
brane by  osmosis,  this  process  being  regulated  by  the  action 
of  the  cells,  similar  to  that  which  takes  place  in  the  lacteals. 

Absorption  by  the  Lymphatics. — That  the  lymphatics 
absorb,  is  perhaps  best  shown  by  the  phenomena  of  disease  ; 
for  example,  the  virus  of  syphilis  is  frequently  carried  from 
the  chancre  on  the  penis,  to  the  glands  in  the  groin,  giving 
rise  to  bubo,  and  the  matter  from  the  abscess  is  capable  of 
imparting  the  disease  to  other  individuals.  The  glands  of 
the  axilla  become  enlarged  and  inflamed,  in  consequence  of 
a  poisoned  wound  of  the  hand  or  arm,  or  in  erysipelas.  Ab- 
sorption takes  place  in  the  same  way,  and  on  the  same 
principle,  as  in  the  lacteals  and  veins.  In  some  animals,  as 
birds  and  reptiles,  the  movement  of  the  lymphis  facilitated  by 
the  action'of  certain  muscular  sacs,  called  lymph  liearts.  The 
function  of  the  lymphatic  vessels  is  to  absorb  the  Ingredients 
of  the  lymph  derived  from  the  metamorphosis  of  the  tissues, 
and  to  return  it  into  the  general  circulation,  in  order  to  sub- 
serve some  further  purpose  in  the  animal  economy,  or  to  be 
eliminated  by  the  process  of  excretion.  They  also  convey 
back  the  superfluous  parts  of  the  material  brought  by  the 
blood-vessels  for  the  supply  of  the  tissues.  The  eflete 
matters  are  not  all  absorbed  by  these  vessels,  for  carbonic 
acid  seems  to  enter  the  capillaries  in  a  direct  manner  through 
their  walls,  since  it  is  found  in  greater  quantity  in  venous 
than  arterial  blood.  The  lymphatic  glands  are  engaged  in 
the  process  of  elaborating  the  lymph  in  its  passage  through 
them. 

The  Glandulcc  Solitaricc  have  been  already  described 
(page  111).  They  are  regarded  as  the  first  row  of  mes- 
enteric glands  situated  in  the  walls  of  the  intestines. 


1 
t 

1 

1 


i'tl 


1G8 


BLOOD. 


CHAPTER  VII. 


ii 


c 

ii: 
ri. 


11 

4^: 


10  i 
11/ 

r!.i'i' 
en, 


BLOOD. 

This  fluid  is  prepared  from  the  food  by  tlie  proces  of  di- 
gestion and  assimilation,  and  is  constantly  circulating 
through  the  vessels,  during  life.  It  supplies  the  material 
from  which  the  tissues  are  built  up  and  nourished  ;  it  con- 
tains the  substance  used  in  the  combustive  process,  and  also 
contains  the  effete  })articlcs  which  result  from  the  disin- 
teirration  of  the  tissues.  The  elements  found  in  the  blood 
may  be  divided  into  four  classes,  as  follows  : — 

1st.  The  elahorative  elements,  as  red  and  white  corpuscles. 
2nd.  The  histogcnetic  elements,  as  albumen,  and  fat.     (Fat 
is  used  to  build  up  the  adipose  and  nerve  tissues.) 

3rd.  The  calorific  elements,  as  sugar  (or  glucose)  and  fats. 

4th.  The  dejyuritic  elements,  as  lactic,  uric,  hippuric, 
and  carbonic  acids,  urea,  creatine,  volatile  fat  acids,  odorous 
substances,  salts,  and  water. 

Quantity. — It  is  very  difficult  to  determine  the  exact 
quantity  of  blood  in  the  human  body  ;  but  from  various  ex- 
periments, it  has  been  ascertained  by  approximation,  that 
the  quantity  of  blood  in  a  human  body  weighing  144  lbs. 
would  be  about  16  or  18  lbs.,  or  as  1  to  8  or  10. 


PHYSICAL   CHARACTER   OF   THE   BLOOD. 

The  blood,  as  it  flows  from  the  vessels,  appears  to  be  a 
homogenous,  red  fluid,  of  a  slightly  alkaline  reaction,  and 
heavier  than  water.  The  odor  resembles  the  perspiration, 
or  the  breath  of  the  animal.  The  temperature  is  about  100° 
F.  The  color  of  arterial  blood  is  bright  scarlet,  and  that  of 
venous  blood  dark  purple  ;  but  disease  of  the  lungs,  heart  or 


MICROSCOPICAL  APPEARANCE. 


16& 


kidney,  may  cause  the  whole  mass  to  assume  a  venous  hue, 
owing  to  the  circulation  of  carbonic  acid  and  other  impu- 
rities in  it ;  or  it  may  as-sume  an  arterial  hue  when  the 
animal  breathes  pure  (jxygen.  It  is  also  stated  by  Dr.  Davy 
that  in  warm  climates  the  blood  is  venous  in  its  character. 
This  is  due  to  the  high  temperature,  which  reduces  the  ex- 
cretion of  carbonic  acid,  and  is  a  fact  of  very  great  ])ractical 
importance  to  the  physician.  The  inhalation  of  chloroform 
or  ether  produces  a  venous  condition,  by  interfering  with 
the  function  of  respiration. 

The  specific  gravity  of  the  blood  varies  from  1050  to  lOoO, 
the  average  being  about  1055.  Any  substance  which  will 
modify  the  relation  between  the  solids  and  fluids  will 
change  the  speciflc  gravity.  For  example,  it  may  be 
diminished  by  the  introduction  of  water  into  the  system, 
whilst,  on  the  other  hand,  it  may  be  increased  by  the  ad- 
ministration of  drastic  purgatives.  In  anemia,  the  specific 
gravity  may  be  increased  by  good  liberal  diet,  and  iron.  The 
specific  gravity  of  the  corpuscles  (solids)  is  1088,  the  liquor 
sanguinis  (fluids)  1028. 


3 

% 


MICRO-5CC^ICAL  APPEARANCE   OF    THE    BLOOD. 

Blood,  when  examined  by  the  microscope,  when  still  in 
the  vessels,  as  in  the  frog's  foot,  or  bat's  wing  is  seen  to 
consist  of  a  solid  and  a  liquid  portion  ;  the  foi'uier  includes 
the  red  and  ivhite  corpuscles,  the  latter,  the  liquor  sangui- 
nis, or  plasma.  On  the  other  hand,  when  the  blood  has 
been  drawn  from  the  body,  and  allowed  to  stand,  it  coagu- 
lates or  separates  into  two  portions — the  oassamentum,  or 
clot,  and  the  serum.  This  coagulation  depends  on  the  pres- 
ence of  fibrin,  which  coagulates  spontaneously,  and  forms  a 
network  of  fibres,  in  the  meshes  of  which  are  included  the  red 
and  white  corpuscles.  The  clot  then  contracts,  and  squeezes 
out  the  serum.  The  crassamentum,  or  clot,  therefore  con- 
sists of  the  fibrin  and  corpu:icles ;  and  the  serum  contains 


c 

c 


R. 


m. 

iuru 


(! 
»» 

!!.■■■ 
IP- 


170  BLOOD. 

the  all'umen,  salts  and  water.      Blood  in  the  living  vessels, 
consists  of 

SOLID.  LUiUID. 

Fibrin \ 

Red  and  White  Corpuscles.  Albumen f  Liquor  Sanguinis, 

Salt.N . . ; I  or  Plasma. 

Water ) 

Blood  out  of  the  body  consists  of 

SOLID.  LKJl'ID, 

i             Albumen ) 
Clot.    Sails >  Serum. 
Water ) 

Blood  Cokpusci-es. — The  human  red   blood  corpuscles 

arc  circular  or  rounded  biconcave  discs,  in  the  centre  of  which 

are  seen  bright  or  dark  spots  according  as  the  microscope  is 

within  or  beyond  focus.  These  spots  which  have  been  mistaken, 

Fiir  <!o.  for  nuclei  (structures  which 

these  corpuscles  do  not  posses 

at  maturity), are  the  result  of 

i'^'^^MTW^^^       the  refraction  of  light.     The 

form,  of  the  disc  may  be 
changed  by  any  agent  which 
^*^^^"  modities  the  si)ecitic  gravity 
of  the  blood,  or  interferes 
with  the  circulation.  For 
exam]ile,  water  is  readily  ab- 
sorbed    by    the     cor})uscle, 

(a)  Human  red  blood  conn.sdes;  (I.)  one  seen  Causiug   it    tO    bcCOmC     OVal, 

edgewise  ;(c)  in  rouleaux  nd.d)  white  eorims-  ,1  rniinrlpfl      nnrl      finnllv 

cles  ;  (e)  white  corpuscle  nndericoiuK  anui:boid  lllCU     lOUnaCQ,     anu     nnaiiy 

chanu^e  of  shape  ;  (0  red  blood  corpuscles  dried  ,      K.^.^f        riiilli  vav  mAntinne 

Bhnuiken  and  crenated  ;  (j;)  red  corpuscles  as  W  OUlSt.       UUUlVei  mCnUOnS 

seen  within  the  focus  of  the   microscope ;  (h)  .i  ^  ^ „/• ^^    i, „,,:.,  ^  j;^J 

the  same  as  seen  beyond  the  focus.  tho  CaSC  Ot  OXCU  haVlUg  died 

from  drinking  too  much  water ;  and  from  the  bursting  of  the 
■  corpuscles,  and  the  liberation  of  the  hemoglobine,  the  ar- 
teries were  stained,  so  as  to  give  rise  to  the  supposition  of 
arteritis.  In  anemia  and  Bright's  disease  they  become  oval, 
and  in  the  latter  case  granular.  When  the  amount  of  fluid 
is  diminished,  or  solids  increased,  as  in  plethora,  the  cor- 
puscles  become   strongly  biconcave   and    ragged    on   the 


MICROSCOPICAL  APPEARANCE. 


171 


borders.  The  inhalation  of  gases  also  produces  a  marked 
change  in  their  shape.  When  carbonic  acid  is  inhaled  they 
become  rounded,  and  are  again  rendered  biconcave  bv 
breatliing  pure  air  or  oxygen  gas.  When  chlcjroform  is  iu- 
lialed  thoy  become  rounded  and  serrated.  Etlier  produces 
an  irregular  outline,  and  the  administration  of  alcohol 
renders  them  oval  and  indented  en  one  side.  A  solution 
of  sodium  chloride  added  to  the  blood,  produces  a  prickly 
condition  of  the  surface  of  the  corpuscles,  like  the  fruit  of  a 
horse-chestnut.  When  acetic  acid  is  added,  they  become 
globular  and  pale,  and  alkalies  cause  them  to  swell  up  and 
disap[)ear.  Tanuiti  (2  per  cent,  solution)  produces  a  small 
projection  or  button  on  some  point  of  the  circumference, 
which  disappears  again  on  the  addition  of  acetic  acid.  The 
corpuscles  may  be  changed  in  shape  during  circulation.  In 
the  capillaries,  they  sometimes  become  elongated,  twisted  or 
bent,  in  order  to  accommodate  themselves  to  the  narrow 
curved  channels  through  which  they  have  to  pass.  They 
consist  of  homogeneous  masses  of  germinal  matter  or  stroma 
infiltrated  by  a  red  coloring  matter,  termed  hemoglobine, 
and  have  no  distinctive  cell  wall. 

The  size  of  the  red  blood  corpuscles  varies  in  the  human 
subject  from  ^-jL_  to  ^-^l_  of  an  inch  (8.3  to  G.2  mmm)  in 
diameter,  the  average  being  about  -'—  (7.1  mmm)  and  the 
thickness  about 


10000 


(2.5  mm.)  The  size  of  the  corpuscles 
bears  no  relation  to  the  size  of  the  animal,  e.  g.,  those  of  the 
mouse  tribe  are  larger  than  those  of  the  deer,  as  will  be  seen 
from  the  following  table  : 


Mim 

Ape — 
Horse . 
Ox. . .  . 
Sheep. , 
Goat., . 
Dog... . 
Rabbit 


7-5Vir(7.i  mmm) 

) 
) 
) 
) 
) 


73^05  (6.5  mmm) 


T5Vo(7-I 

reViT  (5-4 
T5'ao  (6.0 
^5*00  (4-0 

? An  (7-1 
?6V.(j(7-o 


Mouse .. . . 

Cat 

Fox 

Wolf  .... 
Elephant . 
Red  Deer. 
MuskDeer  ytsIits  (2-0 


Ti'oo  (5-7 
tAu  (6.1 

Z^ViTS  (7-0 


)     Sloth TT^ig-^ 

In  all  of  the  above,  the  form  and  appearance  of  the  corpus- 
cles are  the  same,  although  they  vary  much  in  size.     The 

9 


.* 

I 

It 


172 


BLOOD. 


c 
c 


n. 

if. 

*»\ 


(.tt 


'>1.I 


elephant,  and  sloth  {Bradypua  didactylus)  are  the  only 
species  in  which  the  corpuscles  are  known  to  be  larger  than 
in  man.  In  the  camel  tribe  (camel  dromedary  lama)  they  are 
oval  in  shape,  but  do  not  possess  a  nucleus.  In  all  the  ovipa- 
rous vertebrata,  as  birds,  reptiles,  and  fishes,  the  corpuscles 
are  of  a  large  size,  oval  in  shape,  and  contain  granular 
nuclei.  The  nuclei  may  be  distinctly  seen  on  the  addition 
of  acetic  acid,  which  clears  up  the  outer  portion.  The  cor- 
puscle of  the  frog  is  from  — ^ 
ramm)  in  diameter,^ 

Fijr.  61. 
Mammals.  Birds. 


to  -'-  of  an  inch  (25  to  21 

1000  I  a  no  ^ 


Reptiles. 


Fishes. 


Typical  characters  of  the  red-blood  corpuscles  in  the  main  divisions  of  the  Vertebrata 
(modified  from  Gulliver.)     The  average  diameter  in  tlve  longest  axis  is  given  in  each  case. 

Color. — In  a  single  stratum  of  red  corpuscles  no  color  is 
observed,  but  when  two  or  three  are  superimposed  upon 
one  another,  a  reddish  tint  becomes  apparent.  The  color 
depends  partly  on  the  shape  of  the  corpuscles,  but  chiefly  on 


i«.'M 


WHITE  CORPUSCLES. 


173 


the  hemoglobine  they  contain.  They  also  have  a  tendency 
to  adhere  by  their  concave  surfaces  in  the  form  of  rouleaux. 
(Fig.  60,  c).  This  is  peculiar  to  the  red  corpuscles,  and  is 
very  much  increased  in  inflammation.  If  any  of  the  salines 
be  added  to  the  blood,  this  peculiar  tendency  is  in  a  measure 
neutralized. 

White  Corpuscles. — These  are  so  named  on  account  of 
their  white,  or  colorless  appearance.  They  have  a  circular 
outline,  appear  granular  within,  and  are  tolerably  uniform 
in  size,  theird  iameter  being  about  jo^otr  of  an  inch  (8.  mmm.) 
in  warm-bloods,  and  ^^Vn  (10  mmm.)  in  reptiles.  In 
some  of  them  a  nucleus  may  be  distinctly  seen  on  the  addi- 
tion of  acetic  acid ;  in  others  the  nucleus  appears  to  be 
broken  up,  so  as  to  give  the  cell  a  granular  appearance, 
(Fig.  GO,  d).  They  are  more  highly  refractive  than  the  red 
under  the  microscope,  and  are  generally  observed  in  or  near 
the  margin  of  the  field,  while  the  red  are  grouped  together 
in  the  central  part.  When  examined  in  the  circulating 
blood  of  a  frog's  foot,  they  are  seen  to  occupy  the  exterior 
of  the  current,  and  adhere  more  or  less  to  the  walls  of  the 
vessels,  or  appear  to  pass  from  the  centre  to  the  walls  and 
back  again.  The  proportion  of  white  to  red  corpuscles  in 
man,  is  about  one  to  -iOO  or  500;  but  in  inflammation  it  may 
be  one  to  ten.  In  certain  diseases  as  anemia,  leucocy- 
th?emia,  etc.,  the  white  corpuscles  are  relatively  increased. 
In  the  oviparous  vertebrata  the  proportion  is  higher  than 
in  man,  being  about  one  to  sixteen ;  while  in  one  of  the 
vertebrata  (amphioxus)  the  red  corpuscles  are  entirely 
absent.  In  ■'  8  invertebrate  series,  on  the  other  hand,  the 
corpuscles  are  almost  invariably  white,  and  hence  the  so- 
called  white  blood  of  this  class  of  animals.  The  white 
corpuscles  have  the  power  of  spontaneously  changing  their 
shape,  and  of  moving  in  certain  directions,  closely  resembling 
those  of  the  amoeba,  (Fig.  12),  and  hence  termed  amoeboid 
movements,  (Fig.  60,  e.)  This  is  due  to  the  contractile 
property  of  th  i  protoplasm.     The  amoeboid  movements  are 


It 


174 


BLOOD. 


c 
c 


MftJI 


^■•., 
w 

•  r 

rir. 

(.'•'1) 


arrested  by  the  addition  of  water  or  acetic  acid.  The  white 
corpuscles  are  reproduced  by  the  process  of  fission.  The 
blood  also  contains  granules  or  molecules,  -g^ig.^  of  an  inch, 
(3.  inmm.)  in  dianietei',  similar  to  those  found  in  lymph  and 
chyle,  some  of  them  fatty,  and  others  probably  al- 
buminous. 

OiiiGiN  OF  THE  Corpuscles. — The  earliest  blood  cor- 
puscles are  formed  from  the  primordial  cells  in  the  vascular 
tract.  The  embryonic  heart  and  aorta  are  formed  by  the 
arrangement  of  masses  of  the  primitive  cells,  or  germinal 
vesicles,  of  the  mucous  or  vegetative  layer,  in  the  position, 
form,  and  thickness  of  the  developing  vessels  respectively. 
The  external  layer  of  cells  is  converted  into  the  walls  of  the 
vessels,  while  those  in  the  interior  form  the  first  blood 
corpuscles.  The  primordial,  or  primitive  vesicles,  are  large, 
colorless,  spherical  cells,  each  containing  a  nucleus,  nucleolus, 
granular  matter,  and  fat  globules.  These  cells,  gradually 
clear  up,  so  as  to  bring  into  view  the  nucleus, 
become  reduced  in  size,  and  develope  the  coloring  matter 
(hemoglobine)  as  they  pass  into  the  form  of  red  corpuscles. 
The  blood  corpuscles  of  the  human  embryo  thus  formed  are 
circular,  disc-shaped,  full  colored,  and,  on  an  average,  about 
TT^ffir  of  an  inch  (10  mmm.)  in  diameter.  They  each  contain 
a  nucleus  (and  in  some  cases  two),  about  ^^£,'07,  of  an  inch 
(5  mmm.)  in  diameter,  and  slightly  granular.  They  are  re- 
producv^d  by  the  process  of  multiplication  by  subdivision, 
or  fission. 

When  the  liver  begins  to  be  formed  this  multiplication 
of  blood  corpuscles  in  the  mass  of  blood  ceases,  according  to 
KoUiker,  and  a  new  production  of  colorless  nucleated  cells 
takes  place  in  the  vessels  of  the  liver.  These  nucleated  cells 
undergo  a  gradual  change  into  red  corpuscles,  similar  to 
those  of  the  fir  fc  brood. 

After  birth,  when  the  lymph  and  chyle  corpuscles  are 
thrown  into  the  current  of  blood,  they  are  developed  into 
red  blood  corpus'^les,  so  as  to  supersede  tho?^"   formed   as 


DEVELOPMENT  OF  THE  CORPUSCLES. 


175 


above  described.  This  is  evidenced — First  by  the  formation 
of  color,  while  the  chyle  and  lymph  are  passing  through  the 
thoracic  duct,  due  to  the  development  of  hemoglobine. 
Secondly,  by  the  presence  of  corpuscles,  which  appear  to  be 
intermediate  stages  of  development  between  the  lymph 
corpuscles,  and  the  nucleated  red  corpuscles  in  the  blood  of 
oviparous  vertebrata.  Thirdly,  by  the  progressive  tran"'- 
tion  from  lymph  or  white  blood,  to  red  blood,  which  may 
be  observed  in  the  ascending  scale  of  animal  life. 

Development  from  Chyle  and  Lymph  Corpuscles. — 
Kolliker  and  Paget  regard  the  red  blood  corpuscles  as  being 
formed  irom  the  smaller  of  the  lymph  and  chyle  corpuscles 
by  a  gradual  [)rogressive  metamorphosis ;  while  Wharton 
Jones  and  Huxley  maintain  that  they  are  foimed  from  the 
nuclei  al(>~\e,  the  outer  portion  of  the  cells  disappearing  in 
the  change.  The  weight  of  authority,  however,  appears  to 
favor  the  former  opinion.  The  change  from  chyle  and  lymph 
corpuscles  to  red  blood  corpuscles,  takes  place  as  follows  : — 
The  chyle  and  lymph  corpuscle's  are  at  first  nucleated  cells, 
the  nuclei  of  which  are  generally  more  or  less  obscured  by 
the  granular  matter  which  surrounds  them,  (Fig.  59.)  They 
vary  in  size  from  ^^^^  to  ^^-^  of  an  inch,  (10  to  8.1 
mmm.)  in  diameter.  The  granular  matter  clears  up,  and 
the  nuclei  disappear.  They  then  become  flattened  or 
biconcave,  contraction  and  consolidation  of  the  cells  take 
place,  which  reduce  their  size  to  a  certain  extent,  and 
hemoglobine  is  developed. 

The  white  corpuscles  are  also  developed  from  chyle  and 
lymph  corpuscles.  Lymph  corpuscles  are  formed  in  the 
lymphatic  glands,  spleen,  adenoid  tissue,and  medullaof  bone. 
The  red  and  white  corpuscles  are  regarded  by  some  as 
two  distinct  and  complete  forms,  neither  being  capable  of 
metamorphosis  into  the  other,  and  each  having  its  own 
specific  purpose  to  subserve  in  the  ani^aal  economy ;  the 
greater  number  of  chyle  and  lymph  corpuscles  proceeding 
to  the  formation  of  red  corpuscles,  while  a  few  of  them  are 


■I 


wm 


176 


BLOOD. 


c 


% 

I' 

inrue 

w 

a.: 


Its » 

it 

n- 

flM' 


♦Ml 


developed  into  the  white  corpuscles  of  the  blood.  The 
argument  in  favor  of  this  theory  is,  that  the  white  cor- 
puscles have  been  found  in  the  blood  in  a  state  of  decay, 
thus  showing  that  they  were  not  destined  to  proceed  to 
a  higher  development.  By  others  they  are  regarded  as  an 
early  or  embryonic  condition  of  the  red  corpuscles,  or  an 
intermediate  stage  of  metamorphosis  between  the  chyle  and 
lymph  corpuscles,  and  the  red  corpuscles.  The  latter  view 
is  supported  by  the  following  arguments  : 

1st,  The  colorless  corpuscles  are  intermediate  in  shape 
and  general  appearance. 

2nd.  They  are  increased  under  circumstances  un- 
favorable to  normal  changes,  as  in  inflammation,  or  in 
persons  of  weak  health,  as  in  anemia,  leucocythsemia,  and 
in  the  tubercular  diathesis. 

The  red  and  white  corpuscles  are  supposed  by  some  to 
be  developed  directly  from  the  plasma  of  the  blood  in  which 
they  float,  by  the  ordinary  process  of  cytogenesis.  Blood 
corpuscles,  like  other  cells,  have  their  period  of  growth, 
maturity  and  decay,  and  while  some  are  undergoing  the 
process  of  disintegration,  others  are  rising  up  to  take  their 
plac  s.  They  are,  no  doubt,  formed  very  rapidly,  as  is 
evidenced  in  their  rapid  formation  after  great  hemorrha,ge, 
and  their  growth  and  development  may  be  facilitated  by 
the  administration  of  iron,  and  a  liberal  diet.  When  the 
corpuscles  are  beginning  to  decay,  they  generally  present 
at  first  a  granular  appearance ;  after  a  little  they  break 
down,  and  the  contents  disappear.  Many  of  them  may  be 
observed  in  a  granular  state  in  phthisis,  albuminuria,  and 
septic  poisoning. 


CHEMICAL  AND    STRUCTURAL    CHARACTERS  OF    THE  BLOOD, 

Chemical  Composition  of  the  Blood. — The  average 
proportion  of  the  constituents  of  the  blood  in  1000  parts  is 
as  follows : — 


CHEMICAL  COMPOSITION  OF  BLOOD.  177 

Water               784.0 

Albumen  (of  serum)              70.0 

Fibrin 2.2 

Red  corpuscles  (dry)        .         .        .         .         .         ,  130.0 

Fatty  matters 1.4 

Inorganic  Salts  :  Sodium  and  Potassium  Chlorides    .  3.95 
Sodium   Phosphate,     Carbonate    and 

Sulphate     .         .         .         .         .  1.30 

Calcium  and  Magnesium  Phosphates  0.25 

Iron  Oxide  and  Phosphate        .         .  0.5 
Odoriferous  and  coloring  matter,  glucose,  gases,  creatine, 

urea,  and  other  extractive  matters    .        .        ,  6.40 

1000. 

These  proportions  are  subject  to  considerable  variation, 
even  in  health,  depending  on  diet,  mode  of  living,  etc.  The 
proportion  of  the  various  ingredients  may  be  determined  as 
follows : — The  blood,  as  it  flows  from  the  vein,  is  received 
into  two  vessels  of  equal  size,  the  first  and  last  portions  of 
the  whole  amount  into  the  first,  and  the  second  and  third 
portions  into  the  second  vessel,  in  order  that  the  two 
quantities  may  be  nearly  alike,  and  then  weighed.  The 
blood  in  the  first  vessel  is  allowed  to  coagulate;  that  in  the 
second  is  whipped  with  a  bundle  of  twigs,  to  separate  the 
fibrin,  which  is  then  washed  with  water — to  remove  the 
salts,  with  alcohol — to  remove  any  coloring  matter,  and 
with  ether — to  remove  any  fats.  It  is  then  weighed.  The 
clot  which  has  formed  in  the  first  vessel  is  then  taken  out, 
and  after  the  serum  has  drained  away,  it  should  be  weighed. 
From  the  weight  of  the  clot  subtract  the  weight  of  the 
fibrin  obtained  from  the  second  vessel,  and  this  will  give 
the  weight  of  the  corpuscles.  The  amount  of  albumen  may 
be  obtained  by  precipitating  it  from  the  serum,  filtering 
and  weighing.  In  this  way  it  may  be  ascertained  that  in 
100  parts  blocd,  about  78  parts  are  fluid,^and  22  parts  solid 
material.  In  the  latter,  there  are  13  parts  corpuscles,  7 
parts  albumen,  \  part  fibrin,  the  salts,  etc.,  making  up  the 
balance.  In  ordinary  analysis,  the  corpuscles  are  estimated 
at  about  13  per  cent,  by  weight,  of  the  entire  blood.  This 
refers,  of  course,  to  the  dry  corpuscles,  from  which  the 
water  has  been   removed.     But    it   is   easilv   seen,   bv   a 


M 

■it 

It 

I 

i 


178 


BLOOD. 


c 

c 
n. 

!!' 

•  s< 

If 

a:- 

If  s 

II 

u 

•  ». 

«»>■ 

rvr» 


microscopic  examination,  that  the  corpuscles,  in  their 
natural  moist  condition  in  the  blood,  constitute  fully 
one-half  of  the  entire  mass  ;  hence  the  discrepancy  in  the 
analysis  of  different  observers.  Lehmann  and  Schmidt  put 
the  raoisi  corpuscles  at  512  parts  in  1000,  or  about  four 
times  the  weight  as  given  above.  Three  fourths  of  their 
weight,  consist  of  water. 

The  red  blood  corpuscles  are  composed  of  a  transparent 
homogenous  substance  called  the  stroma,  in  which  the 
hemoglohine  is  infiltrated.  The  sti'oma  is  tough  and  elastic, 
and  consists  of  globuline,protagon, fatty  matters,  cholesterine, 
and  salts.  The  most  important  of  these  is  the  glohuline. 
It  is  a  semi-liuid  substance,  belongs  to  the  albuminous 
compounds,  and  is  formed  from  albumen.  It  is  soluble  in 
water,  but  not  in  the  liquor  sanguinis  or  fluid  plasma  of 
the  blood,  and  is  readily  acted  on  by  acetic  acid,  causing 
the  corpuscles  to  swell  out  and  finally  burst..-  It  coagulates 
completely  at  200°  F. 

Hemoglohine  is  a  kind  of  pigment  matter  which  is  found 
in  the  red  blood  corpuscles,  mingled  with  the  stroma.  It 
is  more  abundant  than  any  other  ingredient  of  the  cor- 
pusclea.  [t  belongs  to  the  albuminous  compounds,  being 
developed  from  albumen  or  fibrin,  and  consists  of  C54  H  7 
N16  O21  S.o  Fe.4  the  latter  of  which  is  an  essential  ingredient. 
It  is  soluble  in  water,  dilute  alcohol  and  alkalies,  but 
is  insoluble  in  ether,  strong  alcohol  and  oils.  It  crys- 
talizes  in  rhombic,  or  hexagonal  plates  or  prisms,  form- 
ing the  so-called  blood  crystals.  Although  a  crystalloid, 
and  soluble  in  water,  it  is  not  diffusible,  i.e.,  it  does  not 
pass  through  the  pores  of  an  animal  membrane.  When 
heated,  it  is  decomposed  into  glohuline  Sind  heTriatine.  The 
distinguishing  characteristic  of  hemoglobine  is  its  strong 
affinity  for  ox3'gen,  forming  oxy-hemoglobine,  which  has  a 
scarlet  color ;  this  readily  parts  with  its  oxygen  again  in 
the  presence  of  reducing  agents,  and  assumes  a  j)urple  hue. 
On  these  qualities  depend  its  most  important  physiological 


pre 
th( 


HEMOGLOBINE. 


179 


properties,  viz.,  as  a  carrier  of  oxygen.  This  also  explains 
the  scarlet  color  of  arterial  blood,  and  the  purple  tint  of 
venous.  It  was  formerly  supposed  that  the  scarlet  color  of 
the  blood  was  produced  by  the  oxygen  rendering  the  cor- 
puscles biconcave,  and  the  venous  condition  by  carbonic 
acid  which  made  them  biconvex  or  rounded. 

Fig's.  62  and  63. 


a.  Spectrum  of  oxidizeil  heiuoglobiiie.     t.  Spectrum  of  cieuxidized  liuiimglobine. 

The  two  varieties  of  hemoglobine  may  be  readily  dis- 
tinguished by  the  spectroscope.  A  solution  of  oxy-hemo- 
globine  or  diluted  arterial  blood,  presents  two  absorption 
bands  in  the  spectrum,  between  the  lines  D  and  E,  one  in 
the  yellow  and  the  other  at  the  commencement  of  the  green, 
(Fig.  62,  a).  The  former  is  narrow  and  well  defined,  the 
latter  is  broader  and  not  so  well  marked.  The  spectrum  of 
deoxidized  hemoglobine  on  the  other  hand,  presents  a  single 
absorption  band  intermediate  in  position  between  the  ^r 
two,  (Fig.  63,  b).  When  from  any  cause  the  red  corpuscles 
are  broken  down,  the  hemoglobine  is  set  free,  and  stains  the 
coats  of  the  vessels,  so  as  to  give  rise  to  an  appearance  re- 
sembling arteritis.  Rupture  of  the  corpuscles  may  take 
place  from  drinking  too  much  water,  or  in  low  forms  of 
disease,  as  in  typhoid  fever,  purpura  hemorrhagica,  etc. 


1 
I 

M 


180 


BLOOD. 


c 

c 

»• 

•f.•^ 


I! 

unit 


Distinction  between  Human  and  Animal  Blood. — 
It  is  sometimes  of  the  utmost  importance  in  medical  in- 
vestigations to  distinguish  between  human  blood  and  the 
blood  of  animals.  In  a  fluid,  or  blood  stain,  when  the  cor- 
puscles have  been  dissolved  or  destroyed,  the  presence  of 
blood  may  still  be  determined  by  the  spectrum  of  hemoglo- 
bine,  but  the  distinction  between  human  and  animal  blood 
cannot  thus  be  made.  It  is  only  by  the  use  of  the  micros- 
cope that  this  can  be  determined.  If  the  blood  stain 
be  found  to  contain  oval  nucleated  corpuscles,  it  cannot  be 
human  blood,  but  that  of  a  fowl,  reptile  or  fish.  If,  on  the 
other  hand,  the  corpuscles  are  circular  and  without  nuclei, 
then  it  will  be  impossible  to  say  whether  it  is  human  blood, 
or  the  blood  of  some  animal,  as  the  cow,  sheep,  ape,  dog,  etc., 
whose  corpuscles  are  nearly  of  the  same  size  as  the  human. 

DIFt-ERENCE  BETWEEN   ARTERIAL    AND  VENOUS  BLOOD. 

Arterial  and  venous  blood  differ  from  each  other  in  general 
composition  and  color.  The  analysis  which  has  already  been 
given  is  of  venous  blood.  In  arterial  blood  the  quantity  of 
solid  constituents  of  the  corpuscles  is  less,  but  relatively 
they  contain  more  hemoglobine  and  salts,  and  less  fat.  It 
also  contains  more  oxygen  and  less  carbonic  acid.  The 
liquor  sanguinis  is  richer  in  fibrin,  contains  more  water,  and 
less  albumen.  The  fatty  matters  of  the  serum  are  dimin- 
ished, and  the  extractive  matters  increased.  The  phosphorus 
which  exists  in  the  venous  blood,  is  converted  at  the  lungs 
into  phosphoric  acid,  which  then  unites  with  the  alkalies  of 
the  serum,  as  lime,  potassa,  soda,  magnesia,  etc.,  forming 
phosphates.  Phosphorus  is  used  in  the  building  up  of  nerve 
and  bone  tissue. 

Blood  of  the  Portal,  Renal  and  Hepatic  Veins. — 
Blood  drawn  from  different  parts  of  the  arterial  system  of 
the  same  animal  is  nearly  always  the  same ;  but  great  vari- 
ations exist  in  the  comjiosition  of  the  blood  in  the  different 
parts  of  the  venous  system.    The  portal  vein  contains  blood 


GASES. 


181 


derived  from  the  gastric,  mesenteric  and  splenic  veins. 
During  digestion,  the  blood  of  the  gastric  and  mesenteric 
veins  is  much  diluted,  and  contains  the  soluble  alimentary 
substances  taken  up  from  the  stomach  and  small  intestine, 
as  sugar  (glucose),  albuminose,  etc.  The  fibrin  also  found 
in  these  vessels  is  less  perfectly  elaborated  than  in  the  blood 
in  general,  and  liquifies  soon  after  '  igulation.  On  the 
other  hand,  the  blood  of  the  splenic  vein  shows  a  diminution 
of  the  red  corpuscles,  an  increase  of  the  white  corpuscles, 
and  an  increase  of  the  albumen.  The  fibrin  is  also  increased, 
but  like  that  of  the  gastric  and  mesenteric  veins  it  is  not 
fully  elaborated,  coagulates  imperfectly,  and  liquifies  soon 
afterwards.  The  blood  of  the  re7ial  veins  is  the  purest  in 
the  body,  having,  subsequently  to  its  purification  in  the 
lungs,  been  deprived  of  other  impurities  by  the  kidneys, 
such  as  urea,  creatine,  salts,  etc.  It  contains  less  water, 
the  albumen  is  neutral  in  reaction,  and  the  fibrin  is  scanty 
and  will  not  coagulate,  (Brown  Sequard.)  The  blood  of  the 
hepatic  veins  contains  an  increased  amount  of  sugar  and  fat, 
which  are  formed  during  the  passage  of  the  blood  through 
the  liver.  It  also  contains  less  water,  albumen  and  salts, 
and  more  corpuscles  and  extractive  matter,  than  that  of  the 
poi-tal  vein. 

Gases, — There  is  a  remarkable  difference  in  the  amount 
of  gases  which  arterial  and  venous  blood  respectively  con- 
tain. The  former  contains  from  16  to  20  per  cent.,  by 
volume,  of  oxygen,  while  the  latter  contains  about  12.  The 
quantity  of  carbonic  acid,  on  the  other  hand,  is  from  30  to 
35  per  cent,  in  arterial,  and  from  40  to  50  per  cent,  in 
venous  blood.  The  quantity  of  nitrogen  varies  from  1  to  2 
in  arterial  and  venous  blood  respectively.  There  are  also 
traces  of  ammonia.  The  difference  between  the  amount  of 
oxygen  and  carbonic  acid  respectively  in  arterial  and 
venous  blood,  confirms  the  idea  that  an  exchange  of  oxygen 
for  carbonic  acid  takes  place  in  the  system,  and  an  ex- 
change of  carbonic  acid  for  oxygen  in  the  lungs.      The  red 


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182  BLOOD. 

corpuscles  carry  oxygen  from  the  lungs  to  the  tissues,  and 
return  carbonic  acid  for  elimination.  The  serum  also 
[tossesses  the  property  of  absorbing  or  dissolving  carbonic 
acid.  A  certain  part  of  the  oxygen  is  used  directly  in 
the  formation  of  fibrin,  from  albumen.  The  proper  develop- 
ment of  fibrin  does  not  take  place  when  the  due  aeration 
of  the  blood  is  interfered  with,  as  in  double  pneumonia,  in 
which  case  it  is  very  much  diminished.  The  presence  of 
oxygen  seems  to  I  e  essential  to  the  production  of  fibrin,  and 
it  has  been  shown  by  experiments  on  rabbits,  that  when 
pure  oxygen  is  breathed  the  quantity  of  fibrin  is  very  much 
increased. 

Dr.  Gairdner  examined  the  blood  of  six  healthy  rabbits, 
and  found  it  to  consist  as  follows,  in  1,000  parts  : 

Fibrin 1.65 

Corpuscles 82.35 

Albumen 46. 30 

He  also  examined  the  blood  of  three  of  these,  which  had 
been  exposed  to  an  atmosphere  of  pure  oxygen  for  half  an 
hour,  and  found  it  to  contain  as  follows  : 

Fibrin 2.40 

•  Corpuscles 69. 56 

Albumen 40.23 

Another  of  these  animals  was  exposed  to  the  action  of  an 
electro-magnetic  current  passed  between  the  chest  and  spine, 
which  produced  a  great  acceleration  of  the  respiratory  move- 
ments, and  the  blood  was  found  to  contain  2.9  parts  of  fibrin 
in  a  thousand.  Although  the  corpuscles  appear  to  be  very 
different  in  the  two  tables,  yet  their  relative  amount  in  pro- 
portion to  the  albumen  is  almost  exactly  the  same  in  both 
cases. 

Color. — The  diflference  in  color  between  arterial  and 
venous  blood,  is  due  to  the  hemoglobine  which  the  red  cor- 
puscles contain  and  the  change  of  color  produced  in  it  by  the 
influence  of  oxygen.  It  is  also  partly  due  to  the  change  of 
shape  of  the  corpuscles.  They  are  biconcave  in  arterial  blood, 
and  rounded  in  venous.     The  former  is  produced  by  the  in- 


■■■■ 


^ 


INFLUEhXE  OF  VENESECTION. 


183 


fluence  of  oxygen ;  but  it  may  also  be  occasioned  by  con- 
tact with  some  of  the  salts  in  solution,  without  any 
direct  exposure  to  oxygen.  The  blood  is  darkened  in  color 
by  whatever  tends  to  expand  the  C(M'puscles,  so  as  to  render 
them  rounded,  whilst  it  is  brightened  by  whatever  tends  to 
render  them  biconcave.  For  example,  arterial  blood  is 
darkened  by  the  addition  of  water,  which  swells  out  the 
corpuscles  and  deprives  them  of  some  of  their  coloring 
matter. 


CONDITIONS   WHICH   INFLUENCE   THE   CHARACTER   OF 

THE   BLOOD. 

Influence  of  Venesection. — It  has  been  found  by  ex- 
periment that,  in  bleeding,  the  corpuscles  suffer  most ;  the 
fibrin  is  increased,  and  the  water  taken  awav  is  soon  re- 
placed  by  transudation  from  the  tissues,  so  that  the  specific 
gravity  is  diminished,  as  will  be  seen  from  the  following 
table,  the  result  of  the  analysis  of  the  blood  of  ten  patients, 
by  Becquerel  and  Rodier : 

Ist  BleeJina^.  2nd  Bleeding.    3rd  Bleeding. 

Specific  gravity  of  defihrinated  blood. .  1056.0  1053.0  1049.6 

Specific  gravity  of  Serum 1028.8  1026.3  1025.6 

Water 793-0  807.7  823.1 

Corpuscles 129.2  116.3  99.4 

Albumen 65.0  63. 7  64.6 

Fibrin 3.5  3.8  3,4 

Extractive  and  Salts 7.7  6.9  8.0 

Fatty  Matters 1.6  1.6  1.5 

1000.0       looo.o       1000.0 

From  the  above  it  will  be  seen  that  the  corpuscles  are 
notably  diminished,  and  that.bleeding  has  no  eflect  what- 
ever in  diminishing  the  amount  of  fibrin.  Fibrin  is  in- 
creased in  all  inflammatory  diseases,  and  the  most  copious 
venesection  is  unable  to  check  it,  but  rather  increases  it. 
The  following  table  gives  the  result  of  bleeding,  in  a  case  of 
rheumatism,  from  Christison : 

Water 844 

Solids  of  Serum 93         * 

Corpuscles 57 

Fibrin 4 


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184  BLOOD. 

Influence  of  Starvation  on  the   Blood. — This  is 

somewhat  similar  to  prolonged  venesection.     The  following 

tables  show  the  result  of  bleecding  upon  a  well-fed  dog ; 

and  also  the  same,  in  a  state  of  starvation.     (Todd  and 

Bowman) : 

Number  of  Bleedings. 

1st.  2nd.  3rd.  4th. 

(Water 783.79  810.89  815.18  813.04 

While  being    1  Corpuscles 142.85  "3-54  110.58  106.95 

fed.            J  Solids  of  Serum.     70.94  70.85  69.92  76.01 

(Fibrin 2.42  4.72  4.34  3.99 

After  these  bleedings,  the  animal  was  allowed  to  recover, 

and  was  well  fed  for  about  three  weeks.     He  was  then 

starved  for  about   four  days,  being  allowed  nothing  but 

water,  and  bled  each  day,  with  the  following  result : 

Number  of  Bleedings. 
Tst.  2nd.  3rd.  4th. 

f  Water 804.40        805.44        838.30        849.84 

While  being     1  Corpuscles 121.08         119. 15  87.98  74.21 

starved.          J  Solids  of  Serum.     72.61  71-46  68.46  71.62 

(Fibrin 1. 91  3.95  5.26  5,13 

In  the  latter  case,  the  diminution  of  the  corpuscles  is 
more  marked  than  in  the  former ;  and  it  will  be  observed 
that  the  corpuscles  had  not  entirely  recovered  from  the 
effects  of  the  first  bleeding.  It  will  also  be  observed  that,  in 
both  cases,  there  is  at  first  an  increase  in  the  fibrin,  and  after- 
wards a  diminution — the  latter  being  caused  by  the  diminu- 
tion of  the  red  corpuscles,  and  consequent  non-development 
of  the  fibrin. 

Influence  of  Iron  and  Flesh  Diet  on  the  Blood  — 
The  quantity  of  blood  corpuscles  may  be  increased  by  the 
administration  of  iron  and  flesh  diet.  Fresh  beef  is  the 
best  diet  for  this  purpose.  It  contains  the  most  appropriate 
materials  for  nutrition,  and  is  comparatively  easy  of  diges- 
tion. The  essence  of  beef,  or  beef  tea,  is  still  better, 
especially  when  the  patient  is  very  feeble,  and  the  stomach 
unable  to  digest  solid  food.  In  anemia,  the  corpuscles  have 
been  increased  from  forty  to  sixty,  and  even  ninety  in  a 
thousand,  in  a  few  weeks,  by  this  mode  of  treatment. 


INFLUENCE  OF  AGE  ON  THE  BLOOD. 


185 


Influence  of  Age  on  the  Blood. — During  the  latter 
part  of  foetal  life,  the  solids  of  the  blood,  especially  the  red 
and  white  corpuscles,  are  incieased,  and  remain  high  for  a 
short  time  after  birth.  They  then  gradually  diminish  until 
puberty,  when  they  are  again  increased,  and  remain  so  dur- 
ing the  most  vigorous  period  of  adult  life,  after  which  they 
begin  to  decline,  as  old  age  advances.  The  object  of  these 
changes  in  the  increase  of  solids,  is  to  fit  the  blood  more 
fully  for  the  nourishment  and  growth  of  the  body  at  these 
important  periods,  viz  ;  immediately  after  birth,  at  puberty, 
and  during  the  period  of  ovulation  in  the  female,  and  the 
corresponding  period  in  the  male. 

Influence  of  Sex  on  the  Blood. — The  solid  elements 
of  the  blood,  especially  the  red  corpuscles,  are  increased  in 
the  male.  In  'pregnancy,  the  blood  has  a  lower  sp.  gr.  than 
the  average,  owing  to  the  deficiency  of  red  corpuscles.  On 
the  other  hand,  the  white  corpuscles  and  fibrin  are 
increased,  the  latter  especially  during  the  last  three  months. 
This  may  be  considered  a  wise  provision  of  nature  to  favor 
the  formation  of  clots  in  the  mouths  of  the  open  vessels 
after  parturition  and  the  separation  of  the  placenta,  and  to 
prevent  post-partum  haemorrhage. 

Influence  of  Disease  on  the  Blood. — It  will  be  seen 
from  the  following  table  that  the  principal  constituents  of 
the  blood  may  vary  much,  in  health,  in  different  pei-sons ; 
and  in  the  same  person,  at  diffierent  times.  This  may  be 
due  to  various  causes,  as  the  kind  or  quality  of  the  food, 
habits,  amount  of  exercise,  etc.  According  to  Andral,  the 
variations  may  be  as  follows  : 


Fibrin 

Corpuscles  " 

Solids  of  Serum  " 
Water 
etc.,  etc. 


from      2  to    3^  parts  per  thousand. 

"     no  to  152  "  " 

72  to    88 

760  to  815  "  " 


In  estimating  the  quantity  of  fibrin  in  the  blood  in  dis- 
eased conditions,  it  should  always  be  borne  in  mind  that  it 
may  contain  a  number  of  white  corpuscles.  These  are  very 


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diflGlcult  to  separate,  and  although  not  very  numerous  in  a 
state  of  health,  yet  in  many  diseases,  as  inflammation, 
anemia,  leucocythsemia,  etc.,  they  are  so  much  increased 
as  to  add  materially  to  the  amount  of  fibrin.  There  is 
found  to  be  an  invariable  increase  of  fibrin  in  all  acute 
inflammatory  aflections  of  a  sthenic  kind.  This  augmenta- 
tion is  so  constant,  that  if  more  than  five  parts  of  fibrin  in 
a  thousand  be  found  in  the  course  of  any  disease,  it  may  be 
positively  affirmed  that  some  local  inflammation  is  present. 
The  maximum  proportion  of  fibrin  in  inflammation  may  be 
stated  at  about  13.3  (acute  rheumatism),  the  minimum  5, 
and  the  average  about  7  parts  in  a  thousand.  Even  in 
anemia  and  chlorosis  it  rises  to  6  or  7  in  inflammation.  In 
phthisis  also,  there  is  an  increase,  notwithstanding  the 
deterioration  of  the  blood.  It  is,  no  doubt,  due  to  the 
local  inflammation  going  on  around  the  tubercles.  In 
single  pneumonia  the  fibrin  has  been  found  as  high  as  10.7; 
in  acute  rheumatism,  13.3.  It  is  slightly  increased  in 
all  the  exanthemata.  It  is  also  increased  in  leucocythsemia. 
The  increase  in  the  quantity  of  fibrin  does  not  depend  upon 
the  febrile  condition  present  in  inflammation,  but  upon  the 
inflammation  itself.  For  example,  in  continued  fever  it  is 
lower  than  in  health,  but  if  local  inflammation  arise  in  the 
course  of  the  disease,  the  fibrin  is  at  once  increased.  In 
simple  continued  fever  it  has  been  found  as  low  Pi  1.6.  In 
typhoid  fever  it  may  varj'  from  3.7  to  0.9,  and  in  some  cases 
the  blood  shows  no  disposition  to  coagulate,  the  fibrin  either 
being  entirely  deficient,  or  very  much  lowered  in  vitality. 
In  double  pneumonia  it  is  as  low  as  0.9,  due  to  the  imper- 
fect aeration  of  the  blood.  In  scurvy  it  is  sometimes  in- 
creased, and  sometimes  diminished.  In  cholei*a  the  serum 
is  first  diminished  next  the  albumen,  and  afterwards  the 
fibrin.  The  vomited  matters,  and  substances  passed  by 
the  bowels  are  coagulable  by  heat  and  nitric  acid.  The 
fibrin  is  diminished  in  apoplexy,  due  probably  to  the 
arrest  of  nerve  force.     In  purpura  hemorrhagica  it  is  0.9,  and 


'  I'i  !l  I 


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INFLUENCE  OF  DISEASES  ON  THE  BLOOD.     187 

sometimes  entirely  deficient.  One  of  the  effects  of  a  diminu- 
tion in  the  proportion  of  fibrin  is  a  tendency  to  the  occur- 
rence of  hemorrhage  from  slight  causes,  which  is  difficult 
to  arrest. 

The  amount  of  red  corpuscles  is  subject  to  greater  varia- 
tion within  the  limits  of  health  than  the  fibrin.  In  plethora 
they  may  be  increased  to  180  or  190.  Plethoric  persons 
are  not  on  that  account  more  liable  to  inflammation ;  but 
they  are  very  prone  to  congestion,  especially  of  the  brain, 
and  apoplexy.  This  condition  may  be  easily  remedied  by 
venesection.  The  number  of  corpuycles  may  be  reduced 
from  180  to  144,  or  from  60  to  48  in  one  bleeding.  In 
anemia,  on  the  other  hand,  the  corpuscles  are  diminished, 
in  some  cases  as  low  as  27  in  a  thousand,  but  they  may  be 
rapidly  increased  by  appropriate  treatment.  They  have 
been  increased  in  some  instances  from  40  to  60,  and  even  90, 
in  three  or  four  weeks.  In  diabetes  mellitus,  Bright's 
disease,  disease  of  the  heart,  lead  poisoning,  tuberculosis, 
cancer,  scurvy,  leucocythaemia,  etc.,  they  are  materially 
diminished,  and  often  assume  a  granular  appearance. 

The  colorless  corptuscles  are  said  to  be  increased  in  infl'im- 
mation,  but  it  is  by  no  moans  constant  In  the  disease  first 
pointed  out  by  Dr.  John  Hughes  Bennett,  of  Edinburgh,  and 
termed  by  him  leucocythsemia,  they  are  largely  increased. 
In  this  disease  the  specific  gravity  of  the  blood  is  low,  and 
the  fibrin  is  invariably  increased. 

The  quantity  of  alhv,men  seems  to  vary  very  little.  It  is 
reduced  in  cholera,  albuminuria,  etc.,  so  that  the  entire  solids 
of  the  serum  have  been  found  in  some  cases  as  low  as  52  in 
a  thousand.  The  diminution  in  the  amount  of  the  albumen 
in  the  serum,  in  albuminuria,  is  exactly  proportioned  to  the 
quantity  found  in  the  urine. 

The  fatty  matters  are  very  much  increased  in  some  in- 
stances, so  as  to  give  the  serum  i.  milky  appearance,  as  for 
example  in  tuberculosis,  Bright's  disease,  hepatitis,  dropsy, 

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etc.,  and  also  during  lactation  in  the  female.  Very  little  is 
known  regarding  the  variations  of  the  alkaline  salts  in 
disease. 

The  proportion  of  water  varies  according  to  the  amount 
of  solids,  being  increased  when  the  solids  are  diminished,  and 
vice  versa.  In  cholera,  however,  the  drain  is  very  great, 
and  the  reduction  of  the  watery  portion  is  most  marked. 

Blood  Poisons. — Substances  which  should  be  excreted 
from  the  body,  as  carbonic  acid,  urea,  bile,  etc.,  may  be 
retained  in  the  circulating  current,  and  be  attended  with 
serious  and  sometimes  fatal  results.  The  most  serious  cases 
of  blood  poisoning,  however,  are  those  in  winch  the  poison 
is  introduced  from  without,  producing  fermentation  of  the 
mass  of  blood,  and  destroying  its  vitality,  as  the  poison  of 
malignant  pustule,  typhoid,  glanders,  venom  of  serpents,  etc. 

coagulation  and  vital  pmoperties  of  the  blood. 

The  blood  is  the  pabulum  of  all  the  tissues  of  the  body. 
It  is  a  living  fluid,  which  possesses  the  power  of  reproduc- 
ing and  maintaining  itself,  and  contains  all  the  elements 
necessary  for  the  supply  of  the  tissues,  and  nothing  dele- 
terious or  poisonous;  for  the  presence  of  pus,  urea,  venom 
of  serpents,  or  septic  poisons,  would  be  alike  destructive  to 
the  vitality  of  the  blood,  and  also  the  tissues.  It  has  a 
certain  amount  of  vi-scidity,  which  seems  neces.sary  to  its 
free  circulation  through  tl  e  capillaries.  Besides,  it  is 
observed  that,  when  from  any  cause  the  albumen  and 
fibrin  are  diminished,  there  is  a  strong  tendency  to  transu- 
dation of  the  watery  portions  of  the  blood,  resulting  in 
dropsies  in  different  parts  of  the  body.  The  corpuscles  are 
the  vital  elements  of  the  blood,  and  they  endow  certain 
other  elements,  such  as  fibrin  and  albumen,  with  vital 
properties.    . 

The  coagulation  of  the  blood  consists  in  a  new  arrange- 
ment of  ^ts  constituents,  which  occurs  when  tlie  blood  is 
removed  from  the  vessels,  or  when  the  body  itself  dies.     It 


COAGULATION. 


189 


depends  upon  the  spontaneous  coagulability  of  the  fibrin, 
(or  its  constituent  elements),  during  which  it  forms  a  net- 
work of  fibres,  in  the  meshes  of  which  are  included  the 
corpuscles,  in  groups,  like  small  piles  of  money.  These  are 
somewhat  more  numerous  near  the  boUom  of  the  clot. 
This  crassamentum,  or  clot,  then  contracts,  aud  squeezes 
out  the  serum,  which  contains  the  water,  albumen  and  salts. 
The  corpuscles  exercise  a  certain  influence  in  the  coagula- 
tion of  the  blood,  but  their  immediate  presence  is  not  abso- 
lutely necessary  to  its  performance.  This  may  be  shown 
by  filtering  frog's  blood,  diluted  with  thin  syrup,  on  a  fine 
paper  filter,  by  which  the  corpuscles  are  kept  back,  and  the 
liquor  sanguinis  which  passes  through,  will  afterwards 
coagulate.  This  is  due  to  the  vitality  which  it  carries  with 
it  from  the  blood  corpuscles. 

When  coagulation  is  observed  under  the  microscope, 
there  are  first  seen  minute  granules  which  aggregate  to 
form  star-shaped  spots  ;  these  send  out  arms  or  [)rojections 

Fig.  64. 


Clot  of  fibrin  containing  blood  Vorpiiscles  entangled  in  its  meshes. 

in  different  directions,  which  are  formed  by  the  addition  of 
granules  in  a  linear  manner.  In  this  way  the  whole  mass 
is  converted  into  a  fibrous  net-work,  enclosing  the  corpus- 
cles in  its  meshes  (Fig.  64). 

The   period  required  for  coagulation   varies   much.     It 
commences  about  two  minutes  after  the  blood  is  drawn,  and 


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18  completed  in  from  half  an  hour  to  two  hours  aftei  wards ; 
but  continues  to  contract  for  many  hours.  The  degree  of 
regularity,  and  the  completeness  of  the  coagulation,  depends 
on  the  previous  elaboration  of  the  fibrin,  and  the  character 
of  the  surface  on  which  it  takes  place,  whether  dead  or 
living,  warm  or  cold,  moist  or  dry,  etc.  It  is  not  generally 
supposed  to  become  organized.  When  it  coagulates  in  the 
open  mouths  of  vessels,  as  in  the  arrest  of  hemorrhage 
from  wounded  arteries,  the  coagulum  is  absorbed  and 
canned  away,  after  the  vessels  have  been  closed,  by  the 
effusion  and  organization  of  lyijph. 

Fibrin  does  not  exist  as  such  in  the  blood,  but  is  supposed 
to  be  formed  in  the  process  of  coagulation,  by  the  union  of 
two  previously  existing  albuminous  substances,  Jibrin- 
oplastin  {or  paraglohulin),  and  Jihrincgen,  united  under 
the  influence  of  a  "  ferment "  formed  in  the  blood  after  its 
removal  from  the  body.  This  is  the  theory  of  Schmidt. 
As  the  basis  of  this  theory  it  has  been  observed  that  if 
blood-serum,  or  the  fluid  of  hydrocele,  or  any  serous  effus- 
ion, be  added  to  any  other  similarly  constituted  fluid,  as 
the  fluid  of  ascites,  or  from  the  pleural  cavity,  coagulation 
takes  place,  resulting  in  the  production  of  fibrin.  Another 
theory  is  that  of  Denis,  according  to  which  a  substance 
exists  in  the  blood,  termed  'plasmine,  in  the  proportion 
of  25  parts  per  thousand,  which  separates  into  two  sub- 
stances when  removed  from  the  body.  One  of  these  is 
fibrin,  which  coagulates,  and  the  other  is  metalbumen, 
which  remains  in  solution.  Plasmine  however,  is  regarded 
by  some  as  a  mixture  of  fibrinoplastin  and  fibrinogen. 

Cupped  and  Buffed  Condition  of  the  Blood. — This 
condition  of  the  blood  generally  occurs  in  inflammation,  but 
is  not  exclusively  confined  to  it,  for  it  has  been  found  to 
occur  in  anemia  and  in  the  blood  of  pregnant  women  during 
the  last  three  months  of  gestation.  It  is  occasioned  by  the 
increased  tendency  of  the  red  corpuscles  in  these  cases  to 
run  together  and  sink   to   the  bottom  of  the  vessel,  and 


COAGULATION. 


191 


thus  leave  the  fibrin  in  the  upper  part.  The  fibrin  then 
contracts  very  firmly — a  circumstance  which  is  favored  by 
the  comparative  absence  of  the  corpuscles — and  in  conse- 
quence of  this  contraction  taking  place,  first  on  the  surface 
and  sides  of  the  clot,  and  thence  extending  internally,  it 
causes  it  to  assume  a  concave,  or  cupped  appearance,  both 
on  the  surface  and  sides.  The  "  huffed  "  appearance  is  due  to 
the  predominance  of  the  fibrin  in  the  upper  part  of  the  clot, 
the  characteristic  color  of  which  is  light  yellow  or  huff. 
The  clot  also  contains  some  white  corpuscles  in  its  meshes, 
and  thorj3  are  said  to  be  increased  in  inflammation.  The 
formatioi^  of  the  cupped  and  huffed  coat,  though  favored 
by  slow  coagulation,  is  often  observed  in  cases  where  the 
coagulation  is  more  rapid  than  usual. 

This  condition  of  the  blood  is  due,  either  to  an  absolute 
increase  of  fibrin,  the  corpuscles  remaining  the  same  ;  or  to  a 
diminution  of  the  corpuscles,  the  quantity  of  fibrin  remain- 
ing the  same  as  in  health.  It  has  also  been  observed  that, 
although  the  clot  is  firmer  in  inflammation,  each  single  fibre 
is  weaker  and  more  easily  broken  down  than  that  of  a 
healthy  clot.  This  is  supposed  to  be  due  to  the  comparative 
absence  of  the  corpuscles,  from  their  having  sunk  to  the 
bottom  of  the  vessel  d^.ring  the  process  of  coagulation 

Circumstances  which  Promote  Coagulation.  —  The 
natural  temperature  of  the  hody,  from  which  the  blood  is 
taken  (in  man  98°  to  100°F.)  is  most  favorable  to  coagula- 
tion. Rest  favors  coagulation,  but  is  not  the  cause,  as  some 
have  supposed  ;  for,  although  at  rest,  if  air  he  excluded,  as 
when  it  is  within  the  living  vessels,  or  covered  with  oil, 
coagulation  is  retarded  for  a  considerable  time.  Exposure 
to  air  accelerateo  the  process  of  coagulation ;  it  takes  place 
more  readily  in  shallow  vessels  than  in  deep  narrow  ones. 
Also,  the  multiplicity  of  points  ;  as  in  a  lacerated,  ragged 
wound,  coagula  are  more  ^eadily  formed  than  in  clean,  in- 
cised wounds.  The  addition  of  less  tlian  twice  its  bulk  of 
water  will  promote  the  coagulation  of  the  blood. 


t 
.% 


192 


BLOOD. 


c 

n. 

»'• 

Vt\. 

H»i 

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p. 

II- 

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tU 


il  Zoiv  state  of  vitality  cf  the  vessels,  from  whatever  cause, 
favors  the  formation  of  clots,  or  embolia,  as  they  are  called. 
These  are,  no  doubt,  frequently  formed  during  life,  as  grooves, 
marked  out  by  the  current  of  blood,  may  be  observed  in 
clots  found  in  the  heart  after  death. 

The  contact  of  foreign  matter  promotes  coagulation,  even 
in  the  living  vessels.  Simon  carried  a  single  thread,  by 
means  of  a  fine  needle,  through  a  contiguous  artery  and 
vein,  and  allowed  it  to  remain  from  twelve  to  twenty-four 
hours.  A  coagulum  was  formed  in  both  artery  and  vein, 
that  in  the  artery  being  pyramidal  in  shape,  the  base 
directed  towards  the  heart,  while  that  in  the  vein  was 
larger  and  more  irregular,  the  clot  being  chiefly  collected  on 
that  side  of  the  thread  most  remote  from  the  heart. 

The  contact  of  dead  animal  matter  accelerates  coagula- 
tion in  a  remarkable  degree,  either  v/ithin  or  without  the 
living  vessels.  The  presence  of  pus  will  produce  coagula- 
tion in  healthy  blood,  in  from  two  to  five  minutes,  and 
when  injected  into  the  veins  it  produces  instantaneous 
death.  When  an  artery  gives  way  in  the  interior  of  an 
abscess,  the  hemorrhage  is  restrained,  to  a  certain  extent, 
by  the  presence  of  the  pus  which  surrounds  it. 

Circumstances  Which  Retard  Coagulation. — In  some 
instances  it  would  appear  that  the  blood  does  not  coagulate 
after  death  ;  for  example,  it  was  stated  by  Hunter,  that  in 
animals  hunted  to  death,  killed  by  lightning,  electric 
shocks,  or  blows  on  the  epigastrium,  the  blood  did  not 
coagulate  ;  but  it  is  probable  that,  even  in  these  cases,  it  is 
only  retarded,  and  ultimately  coagulates,  though  imperfectly. 
It  is  further  stated,  by  Polli,  that  the  blood  invariably 
coagulates  before  putrefaction  sets  in.  Nevertheless,  in 
cases  of  poisoning  by  hydrocyanic  acid,  and  in  death  from 
asphyxia,  coagulation  may  not  take  place,  in  consequence 
of  the  complete  paralysis  of  the  corpuscles  and  fibrin.  In 
inflammatory  conditions  the  blood  drawn  is  usually  slow 
in  coagulating,  in  consequence  of  the  sinking  of  the  cor- 


I 


COAGUIATION. 


193 


puscles  ;  but  the  clot  is  preternaturally  firm,  especially  at 
the  upper  part,  where  the  buffy  coat  contracts,  and  produces 
the  "  cupped  condition,"  whicli  generally  indicates  a  high 
state  of  inflammation.  The  coagulation  of  the  blood  is 
retarded,  or  altogether  destroyed,  by  keeping  it  at  a  <em- 
perature  o/120°F.,  while  th-^  natural  heat  of  the  body  (98" 
F.)  promotes  it.  It  is  also  retarded  by  cold,  but  is  not 
destroyed,  even  by  freezing ;  for,  if  frozen  as  soon  as  it  is 
drawn  from  the  vessels,  it  will  coagulate  on  being  thawed. 
The  addition  of  more  than  huice  its  bulk  of  luater  retards 
the  coagulation  of  the  blood.  Continued  agitation  also 
retards  the  coagulation  for  a  time  ;  but  it  ultimately  takes 
place  in  the  form  of  shreds,  or  strings.  Blood  while  still 
contained  in  the  living  vessels,  or  effused  in  the  living' 
tissues,  may  continue  in  a  fluid  condition  for  a  long  period. 
Gulliver  states  that  the  blood  included  between  two  ligatures 
in  a  living  vessel  remained  fluid  three,  four,  or  five  hours. 
He  also  mentions  one  remarkable  case,  in  which  blood  effused 
in  the  tissue  of  the  loin,  was  found  fluid  when  let  out  twenty 
eight  days  afterv/ards.  In  all  these  cases  it  coagulated  in. 
from  fifteen  to  thirty  minutes  when  withdrawn  from  the 
livicg  parts.  Exclusion  from  the  air  retards  coagulation,. 
as  may  be  seen  by  covering  the  blood  with  a  stratum  of  oil 
so  as  to  exclude  the  air.  The  addition  of  alkaline  or  earthy 
salts,  added  to  fresh  blood,  have  a  tendency  to  retard,  and 
sometimes  to  prevent  coagulation ;  and  the  same  effect  is 
produced  by  many  vegetable  substances,  especially  those  of 
the  narcotic  and  sedative  class,  as  opium,  hyoscyamus,  bella- 
donna, aconite,  digitalis,  etc.  Gulliver  mentions  that  he  has 
kept  horses'  blood  in  a  fluid  state  for  fifty-seven  weeks,  with 
solution  of  potassium  nitrate,  and  that  it  still  coagulated, 
when  diluted  with  water.  The  presence  of  bile  retards  the 
coagulation  of  the  blood ;  and  septic  or  animal  poisons  as 
the  virus  of  serpents  may  retard  or  entirely  destroy  its 
coagulating  power.  It  is  also  retarded  by  imperfect  aera- 
tion of  the  blood  during  life,  as  in  asphyxia. 


1 

it 
<t 

i 


194 


ILOOD. 


c 

g: 
I. 

m\ 


4. 

n- 

•  »»,■; 

CKJ' 


FUNCTION  OF  THE  CONSTITUENTS  OF  THE  BLOOD, 

Function  of  Fibrin. — It  was  formerly  supposed  that 
fibrin  was  that  element  of  the  blood  which  was  directly 
drawn  upon  in  the  process  of  nutrition.  This  opinion  was 
based  on  the  then  current  theory  that  fibrin  and  muscle 
were  identical  in  chemical  composition  ;  but  it  has  since 
been  shown,  by  Liebeg,  that,  so  far  from  this  being  the 
case,  the  evidence  is  precisely  the  other  way.  There  is  no 
evidence  whatever  that  fibrin  (or  its  constituent  elements) 
is  used  in  the  foi-mation  of  any  of  the  tissues,  while,  on 
the  other  hand,  there  are  negative  evidences  that  their  for- 
mation and  growth  do  not  depend  upon  its  presence. 
Firstly,  the  general  purposes  of  nutrition  may  be  served  by 
a  fluid  which  does  not  possess  the  property  of  coagulating 
spontaneously.  Secondly,  the  small  amount  of  fibrin  found 
in  the  chyle  is  simply  the  result  of  elaboration  in  the  lym- 
phatics. Thirdly,  the  vegetable  cell,  which  is  essentially 
the  same  as  the  animal  cell,  is  formed  from  an  albuminous 
fluid,  there  being  no  fibrin  in  the  juices  of  the  plant.  As 
a  component  of  the  blood,  fibrin  is  of  importance  in  giving 
it  its  j^roper  degree  of  plasticity,  and  in  this  way  facilitat- 
ing its  ilow  along  the  vessels.  It  also  prevents  the  blood 
from  exuding  through  the  coats  of  the  vessels,  and  arrests 
hemorrhage  by  plugging  up  the  mouths  of  the  open  ves- 
sels. The  want  of  the  coagulating  power  of  the  blood  is 
strikinj^ly  seen  in  cases  of  purpura,  hemorrhagiri,  in  which 
the  Mood  is  not  able  to  form  a  clot  sufF  jient  to  close  the 
mouth  of  the  smallest  vessel,  or  to  form  a  barrier  to  sur- 
round abscesses,  and  prevent  the  infiltration  of  pus  in  the 
tissues.  The  same  thing  may  be  seen  in  the  hemorrhagic 
diathesis,  in  which  there  is  almost  an  entire  absence  of 
coagulable  material.  Fibrin  was  formerly  supposed  to  be 
the  material  thrown  out  in  the  healing  of  wounds,  and  in 
the  formation  of  adhesive  bands  in  inflammation. 

Some  physiologists  and  pathologists,  among  whom  are 
iJimmerman,   Simon,  Jones  and  Sieveking,  etc.,  have  ad- 


V£ 

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E UNCTION  OF  THE  RED  CORPUSCLES. 


195 


vanced  the  idea  that  fibrin  should  be  regarded  as  among 
those  substances  which  have  arisen  from  the  decay  of  the 
blood,  or  the  effete  matter  thrown  into  it  from  the  tissues. 
In  support  of  this  view  they  advance  the  following  argu- 
ments. First,  that  fibrin  is  increased  in  bleeding,  starva- 
tion, anemia,  and  other  states  of  exhaustion,  while,  at 
the  same  time,  the  red  corpuscles  are  rapidly  reduced  by 
the  same  means.  This  view  is  also  favored  by  the  fact  that 
in  improvement  of  the  breed  of  animals,  the  red  corpus- 
cles are  increased,  and  the  fibrin  diminished.  Secondly, 
there  is  only  a  small  quantity  of  fibrin  in  fcetal  blood,  and 
in  the  renal  veins ;  none  in  the  egg,  or  the  chyle  until  it 
enters  the  lacteals ;  and  it  is  also  smaller  in  quantity  in  the 
blood  of  the  carnivora  than  in  the  hcrbivora. 

Function  of  the  Red  Corpuscles. — One  great  function 
of  the  red  corpuscles  is  to  elaborate  the  ipateriais  of  the 
blood  which  are  to  be  used  in  the  nutrition  of  the  tissues, 
more  especially  those  which  sup]»ly  the  muscular  and  nerve  " 
tissues.  They  also  assist  in  converting  the  albumen  into 
fibrin,  and  in  forming  globuline  and  hemoglobine  from  the 
albumen  and  fibrin  of  the  blood.  They  are  also  carriers  of 
oxygen  to  the  tissues,  and  deporters  of  carbonic  acid  from  the 
tissues  to  the  lungs,  where  it  is  eliminated.  The  former  is 
due  to  the  aflinity  of  hemoglobine  for  oxygen.  In 
anemia,  when  the  corpuscles  are  very  much  diminished,  the 
strength  of  the  individual  is  correspondingly  reduced. 

The  number  of  red  corpuscles  bears  a  close  relation  to 
the  amount  of  respiratory  power  in  the  different  clas.ses  of 
vertebrata  :  both  of  these  are  also  found  to  be  greatest  in 
birds,  less  in  mammals,  and  very  low  in  most  reptiles  and 
fishes.  The  i)roportion  of  the  corpuscles  is  greater  among 
the  carnivora  than  the  herbivora.  The  want  of  red  corpus- 
cles in  the  invertebrata  is  compensated  by  the  introduction 
of  air  through  their  tracheal  apparatus,  directly  to  the 
tissues  themselves. 


19(J 


BLOOD. 


C' 

c 

MM 

i: 

»^ 


«; 


It* 

II 

«»" 

c»a 


Function  of  tifk  Wiiitk  Corfuscles. — Thcso  aro,  no 
(l()ul)t,  nisi)  coiicoriiod  in  tlu>  olahoration  of  nutrient  ninturial 
for  the  tissues  of  tlio  Ixxly,  nioro  ospocially  in  tlio  in- 
vortobrato  classes  of  animals.  Tlicso  corpuscles,  which 
arc  oat-shapt'«l  in  the  larvai  of  insocts,  aro  found  nioro 
numerous  just  before  each  chanfje  of  skin,  at  which  time  a 
lai'f^er  supply  of  nouiiNlnucnt  is  iHMpiircd.  After  theso 
changes  have  taken  place,  they  are  again  diminislied.  Tho 
white  corpuscles  also  contain  a  small  (pumtity  of  iron,  thus 
allowing  that  th(>  characteristic  color  of  tht5  hmI  corpuschis  is 
not  due  to  this  substance.  In  the  V(>rtebrata,  on  tho  other 
hand,  the  excess  of  colorless  coipuscles  is  an  evidence  of  un- 
healthy action;  lor  exam])le,  they  aic  very  nbutidant  in  tho 
blood  of  frogs  that  aro  youtig,  sickly,  or  ill-fed.  In  tho 
human  subject,  they  are  incicascd  in  tho  disease  called  leu- 
cocythiiMuia,  in  anemia,  and  also  in  intlatnjiiation  aceoiding 
to  some,  although,  in  all  probability,  this  only  occurs  in 
sickly,  scrofulous,  or  tuberculous  patients.  When  the  cir- 
culation of  the  blood  is  examined  in  a  bat's  wing,  or  frog's 
foot,  under  the  microscope,  the  white  corpuscles  may  bo  ob- 
servctl  running  from  the  centre  of  the  current  to  tho 
circumference,  and  back  again,  and  occasionally  adhering  to 
the  sides  of  tho  vessehs.  They  may  also  be  occasionally  seen 
passing  through  the  coat^s  of  the  vessels  by  virtue  of  their 
anuTeboid  movements,  or  iliapedesif^.  In  this  process  they 
throw  out  arms  or  projections  which  enter  the  pores  of  tho 
vessels  and  gradually  force  their  way  through.  They  thus 
pass  out  in  large  numbers  in  the  healing  process,  and  in  in- 
tiammation,  and  are  supi>osed  to  form  the  lymph.  In  this 
they  arc  supplemented  by  the  proliferation  of  connective 
tissue  cells  in  the  inflamed  or  wounded  parts. 

Function  of  Albumen. — This  substance  is  the  ))abuUim, 
from  which  the  tissues  of  the  body  are  formed.  It  is  also 
used  in  the  formation  of  the  fibrin,  globuline,  and  hemoglo- 
bine  of  the  Wood  itself.  Albumen  by  itself,  however,  is  in- 
capable of  organization,  and  its  conversion  into  the  various 


FUNCTION  OF  FATS  IN  THE  BLOOD. 


197 


tiH8tioa  must  (lopoTid  on  tlioir  owd  power  of  appropriation. 
It  also  assists  in  holding  in  solution  in  tho  blood  many  of 
tho  metallic  salts  which  exist  in  that  lluid,  or  which  enter 
tho  system,  Tho  all)uin«!n  is  «lerived  from  tho  food,  and 
when  any  excess  is  taken  into  the  s3'stem,  it  undergoes  a 
retrograde  change,  and  is  eliminated  l»y  the  liviir  and  kidney. 
It  is  not  excreted  in  health,  but  may  be  found  >n  the  urine 
in  certain  <liseased  conditions,  as  morbus  Brightii,  scarla- 
tina, etc.  its  presence  in  tho  inino  nuiy  bo  detected  by 
heat  and  nitric  acid,  which  cause  a  j>recipilate  in  the  form 
of  Hakes.  It  may  also  bo  bund  in  the  voTnifa  and  dejecta 
in  cholera  and  yellow  fever. 

Fats, — The  fatty  matters  taken  into  tho  system  are  in^ 
tended  in  part,  for  tho  supj)ly  of  tho  adi|)')so  and  n«;rvo 
tissu<; ;  but  their  chief  use,  liowever,  is  to  afford  material  for 
that  couibustivo  |)rocess  wliich  is  necessary  for  the  main- 
tenance of  animal  heat.  It  also  contributes  to  the  formation 
of  milk.  That  which  is  stored  up  in  the  body  nmy  be 
looked  U[)on  as  tho  suiplus.  Fat  is  often  detected  in  i\\Q 
fioce.s,  and  such  cases  indicate  a  diseased  condition  of  the 
liver  or  pancreas. 

The  other  organic  compounds  which  have  been  found  in 
the  blood,  as  sugar,  lactic  acid,  urea,  uric  and  hipi)uric  acid.s, 
creatine,  creatinine,  fatty  acids  and  odorous  substances,  but 
which  do  not  properly  form  a  ])art  of  it,  are  the  result  of  a 
retrograde  metamorphosis,  either  of  the  alimentary  sub- 
stances or  of  the  ti.ssue^  themselves,  and  are  rajjidly  elimi- 
nated by  the  lungs,  kidneys,  liver,  .skin,  etc. 

IVie  uses  of  the  inorganic  salts  are  not  positively  known  ; 
but  such  as  have  been  investigated  were  '^ferred  to  in  the 
chapter  on  the  proximate  principles  oi  the  first  class,  Tho 
alkaline  salts  as  sodium  and  potassium  carbonates  and 
phosphates  are  necessary  to  give  the  olood  its  alkalinity,  to 
hold  in  solution  the  albumen,  and  to  facilitate  the  passage 
of  the  blood  through  the  capillaries,  The  salts  are  necessary 
also  for  the  proper  nutrition  of  the  muscular  tissue.     Lime 


% 

i 


198 


BLOOD. 


c 

A. 

m 


ma* 


•ft* 

■»' 


II 

BW.1 

rut 


phosphate,  lime  carbonate,  calcium  fluoride,  etc.,  are  re- 
quired to  build  up  the  solid  tissues,  as  bone,  teeth,  etc.  The 
lime  phosphate,  in  particular,  may  be  regarded  almost  as  a 
histogenetic  substance,  as  it  seems  to  be  almost  invariably 
present  in  newly-forming  tissues,  but  more  especially  in  the 
bone  and  teeth.  Iron  is  an  essential  ingredient  of  the  blood 
itself,  entering  into  the  f>rmation  of  the  hemoglobine. 
Water  exists  in  large  quantities,  and  is  liable  to  consider- 
able variation. 

RELATION  OF  THE  BLOOD   TO   THE   LIVING    ORGANISM. 

The  normal  proportions  of  all  the  substances  found  in  the 
blood  are  maintained  partly  by  the  selective  power  of  the 
tissues  in  the  process  of  nutrition  and  growth,  and  partly  b}' 
means  of  tlie  excretory  apparatus,  which  removes  the  surplus 
materials.  Each  part  of  the  body  takes  from  the  blood  the 
peculiar  substance  which  it  requires  for  its  nutrition,  and 
thereby  acts  as  an  excretory  organ,  by  removing  that,  which 
if  allowed  to  remain  in  the  blood/would  act  injuriously  in  the 
nutrition  of  the  body  generally;  for  example,  the  phos- 
phates and  carbonates  which  are  deposited  in  the  bones  are  as 
effectually  removed  from  the  blood  as  those  which  are  thrown 
off  by  the  urinary  organs.  Again,  the  rudimentary  organs, 
as  the  hair  in  the  foetus,  the  mammse  in  the  male,  etc.,  may 
be  looked  upon  as  excretions  serving  a  useful  p  irpose  in 
the  animal  economy,  by  removing  certain  materials  from 
the  blood  which  might  interfere  with  the  proper  nutrition 
of  other  parts  of  the  body. 

Although  the  blood  may  vary  slightly  in  its  composition 
and  properties  at  different  periods  of  life,  yet  we  find  that, 
taken  as  a  whole,  it  presents  such  a  constancy  in  iti  leading 
features,  that  we  cannot  fail  to  recognize  in  it  some  capacity 
for  self-development,  similar  to  that  which  the  solid  tissues 
possess.  It  retains  its  identity  through  life,  just  as  a  leg,  an 
arm,  or  an  eye.  It  has  the  power  of  maintaining  itself  from 
the  new  materials  supplied  to  it  from  the  food,  and  goes 


RELATION  TO  THE  LIVING  ORGANISM. 


19i> 


through  the  successive  phases  of  growth,  maturity,  and  de- 
cay, similar  to  all  vital  organisms.  The  self-maintaining 
power  of  the  blood  is  forcibly  exhibited  in  the  phenomena 
of  disease,  especially  those  of  a  febrile  class,  as  the  exan- 
themata, typhus,  typhoid,  etc.  In  all  these  cases  the  "  mor- 
bid poison  "  would  be  eliminated  by  nature,  if  time  were 
allowed  to  do  so,  the  blood  replenished,  and  the  patient 
would  resume  his  wonted  health.  In  some  instances,  when 
a  poisonour\  substance  has  entered  the  blood,  the  life  may  be 
saved  by  keeping  up  artificial  respiration  until  nature  has 
time  to  eliminate  the  poison  from  the  system.  In  nearly  all 
the  toxic  diseases  of  the  zymotic  class,  there  is  a  natural 
tendency  to  self-elimination  of  the  poison,  and  of  the  pro- 
ducts of  its  action  on  the  blood  either  by  the  agency  of  the 
excretory  organs,  or  by  the  local  lesions  which  occur  in  these 
cases,  and  this  occurs  with  such  regularity  that  we  are  able 
to  predict  with  certainty  when  the  changes  may  be  ex- 
pected to  take  place.  From  the  very  nature  of  the  action 
of  these  poisons  on  the  blood,  it  is  evident  that  no  reliance 
whatever  can  be  placed  on  the  action  of  antidotes  in  check- 
ing their  course.  The  object  of  treatment  lies  wholly  in  pro- 
moting the  elimination  of  the  morbid  poison,  in  subduing 
local  action,  and  supporting  the  vital  powers  of  the  patient 
during  the  continuance  of  the  disease. 


1 

I 

i 


s 


500 


CIRCULATION. 


CHAPTER  VIII. 


C 

C 
II. 

« 

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w» 

C 

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I"'' 
t* 

in 
Ifit 

c 

(I 

«ir"  ; ' 

CKic 

ea 


CIRCULATION. 

The  object  of  the  circulation  of  the  blood  is  to  carry  to 
every  part  of  the  body  the  materials  for  its  nutrition  and 
growth,  together  with  the  supply  of  oxygen  necessary  for 
its  vital  actions ;  and  also  to  carry  away  the  effete  sub- 
stances which  are  formed  as  a  result  of  the  waste  of  the 
tissues.  The  organs  concerned  in  this  process  are  the  heart, 
arteries,  veins,  and  capillaries. 

THE    HEART. 

The  heart  is  the  great  central  organ  of  circulation, 
situated  in  the  middle  mediastinum  of  the  thorax,  being 
placed  obliquel}-^,  the  base  upwards  and  to  the  right  side, 
on  a  level  v/ith  the  upper  border  of  the  third  costal  eaitilage 
and  corresponding  to  the  interval  between  the  fifth  and 
eighth  dorsal  vertebrse,  the  apex  corresponding  to  the  inter- 
space between  the  cartilages  of  the  fifth  and  sixth  ribs,  one 
inch  to  the  inner  side;  and  two  inches  below  the  left  nipple. 
It  is  a  hollow,  muscular  organ,  which,  like  a  forcing  pump, 
drives  the  blood  through  the  vascular  systen.  It  weighs 
from  9  to  10  ounces,  and  is  about  equal  to  the  size  of  the 
closed  fist  of  the  individual,  It  varies  in  size  and  shape, 
in  different  classes  of  animals,  from  a  simple,  muscular  tube, 
as  in  insects,  to  the  complex  double  heart  of  man.  In  all 
animals,  the  organs  of  circulation  are  adapted  and  modified 
in  structure  to  correspond  with  the  organs  of  respiration. 
In  the  lower  order  of  animals,  as  insects,  the  heart  consists 
of  a  simple  muscular  tube,  provided  with  certain  valves  at 
short  distances  apart.  Corresponding  to  the  situation  of 
these  valves,  there  are  distinct  constrictiont,  in  the  tube,  so 


THE  HEART. 


201 


that  it  has  the  appearance  of  a  series,  or  chain  of  hearts.  As 
we  ascend  the  scale,  we  first  observe  the  subdivision  of  the 
heart  into  two  cavities,  the  auricles  and  ventricles,  in  the 
acephalous  mollusks.     In  fishes,  also,  the  heart  consists  only 


1  i^.  6P. 


Rijrht  auricle  and  ventricle  opened,  to  show  their  interior.  1,  superior  vena  cava ;  2, 
inferior  vena  cava;  2',  hepatic  veins  ;  3,  right  auricle  ;  3',  fossa  ovalis,  below  which  is  the 
Eustachian  valve  ;  3",  coronary  vein  ;  +,  +,  auriculo-ventricular  groove  ;  4,  4,  cavity  of 
the  right  ventricle,  the  upper  "figure  is  immediately  below  the  seniilimar  valves  ;  4',  large 
columna  carnea  or  musculug  papillaris  ;  5,  6',  5",  tricuspid  valve ;  6,  in  pulmonary  artery  ; 
7,  aortic  arch  close  to  the  ductus  arteriosus  ;  8,  ascending  part  or  sinus  of  the  arch  covered 
at  its  commencement  by  the  auricular  appendix  and  jnilmonary  artery  ;  9,  the  innominate 
and  left  cartoid  arteries;  10,  appendix  of  the  left  auricle  ;  11,  11,  the  outside  of  the  left 
ventricle,  the  lower  figure  near  the  apex. 

of  two  cavities,  the  auricle,  j.ito  which  the  blood  is  received 
from  the  veins,  and  a  ventricle,  which  drives  the  blood  into 
the  main  artery  which  supplies  the  gills.  In  reptiles,  there 
are  two  auricles  and  one  ventricle.     One  of  the  auricles 


c4i 


M 


4 


202 


CIRCULATION. 


c 

MM 


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MM 

in* 


"v. 

p-' 
It. » 

»l 

uru 
»»■:- 
cn.1 


receives  the  blood  from  the  lungs,  the  pulmonic ;  and  the 
other,  the  blood  from  the  veins  of  the  body,  the  systemic 
auricle.  They  both  open  into  a  single  ventricle,  which 
propels  the  blood  throughout;  the  body,  and  also  to  the 
lungs. 

In  birds  and  mammals  (including  the  human  species)  the 
heart  consists  of  two  auricles  and  two  ventricles,  separated 
•by  a  complete  septum,  each  auricle  communicating  with  its 
corresponding  ventricle,  and  v-Jich  ventricle  communicating 
with  an  arterial  trunk.  The  course  of  the  circulation  is  as 
^"'s-  "«  follows  :— The  venous 

blood  is  returned  from 
the  body  by  the  super- 
ior and  inferior  vena^ 
cavse,  and  poured  in- 
to the  right  auricle  ; 
thence  it  passes  into 
the  right  ventricle, 
being  prevented  from 
returning  by  the  clo- 
sure of  the  tricuspid 
valves ;  from  the  right 
ventricle  it  passes  to 
the  lungs,  through 
the  pulmonary  artery, 
the  opening  being 
closed  behind  it  by 
the  coaptation  of  the 
pulmonary  semilunar 
valves.  The  blood 
Diagram  of  the  circulation.  ^^Ing  aerated  in  the 

lungs,  is  returned  to  the  left  auricle  through  the  pulmonary 
veins  ;  this  constitutes  the  pulmonic  circulation.  It  next 
passes  through  the  auriculo-ventricular  opening  into  the 
left  ventricle,  being  prevented  from  returning  by  the 
closure  of  the  mitral  valves  ;  it  is  then  propelled  with  con- 


PROOFS  OF  THE  CIRCULATION. 


203 


siderable  force  into  the  aorta,  the  opening  being  closed 
behind  it  by  the  coaptation  of  the  aortic  semilunar  valves, 
and  is  thence  distributed  to  the  various  parts  of  the  body, 
to  be  again  returned  by  the  veins  to  the  right  side  of  the 
heart.  The  latter  constitutes  the  systemic  circulation.  On 
reference  to  the  diagram  there  will  also  be  seen  a  sub- 
ordinate stream,  or  offset  of  the  general  or  systemic 
circulation  which  passes  through  the  liver ;  this  is  the 
liortal  circulation.  The  variation  in  the  course  of  the  blood 
during  foetal  life  is  called  foetal  circulation. 

Proofs  of  the  Circulation. — The  circulation  of  the 
blood  was  discovered  by  Harvey  in  1618.  The  main 
arguments  by  which  he  proved  the  circulation  were  as 
follows  : —  1,  The  heart  propel.^  in  half  an  hour,  more  blood 
than  the  whole  mass  in  the  body.  2,  The  blood  spurts  iu 
a  jetting  manner  from  a  wounded  artery.  3,  If  true,  the 
normal  course  of  the  circulation  explains  why  the  arteries 
were  found  empty  after  death.  4,  If  the  veins  were  tied 
near  the  heart,  it  became  pale  and  bloodless  ;  if  the  artery 
were  tied,  the  heart  became  distended.  5,  If  a  ligature  be 
drawn  tightly  around  the  limb,  no  blood  can  enter  and  it 
becomes  pale  and  cold  ;  if  slightly  relaxed,  blood  can  enter 
but  cannot  leave  the  limb,  hence  it'swells.  6,  The  existence 
of  valves  in  the  veins,  which  permit  the  blood  to  flow  only 
towards  the  heart.  7,  The  constitutional  disturbance  re- 
sulting from  poisons  introduced  at  a  single  point. 

To  these  may  be  added  proofs  accumulated  since  the  time 
of  Harvey,  viz. :  the  effects  of  wounds  of  arteries  and  veins 
respectively ;  in  the  former  hemorrhage  may  be  arrested 
by  pressure  above ;  in  the  latter,  by  pressure  below  the  seat 
of  injury.  The  direct  passage  of  blood  corpuscles  from 
small  arteries,  through  the  capillaries  into  the  veins,  seen  by 
the  microscope  in  the  web  of  the  frog's  foot,  the  tail  of  the 
tadpole,  etc.  The  injection  of  certain  substances  into  the 
veins,  which  have  been  detected  in  the  arteries  a  short  time 
II 


•4 
% 


204 


CIRCULATION. 


c 

MM 

c 

If' 


1*9 


IV-' 

II- 

Crur 

•  •(:■,. 

tW 
iin.4 


afterwards.     The  valves  of  the  heart  are  also  so  arranged  as 
to  permit  the  blood  to  pass  only  in  one  direction. 

Muscular  Structure  of  the  Heart. — The  heart  con- 
sists of  striated  muscular  fibres,  and  fibrous  rings  which 
serve  for  their  attachment.  The  fibres  are  not  arranjcred  in 
bundles,  but  interlace  with  each  other  in  an  intricate 
manner,  and  adhere  closely  together,  there  being  little  or 


Fig.  67. 


Fijf.  08. 


kSbUs  [  =u^ 


Fig.  C".  Jluscular  fl'ires  of  the  licart,  sliow 
itg  their  stria),  divisions  and  junctions 


none  of  that  areolar  tissue 
whi  h  exists  in  the  external 
muscles,  and  there  is  no 
appearance  of  sarcolemraa. 
The  fibres  are  also  small  n* 
than  those  of  other  parts  of 
the  body,  and  the  strise  are 
less  marked.  The  dispo- 
sition of  the  fibres  of  the 
heart  may  be  demonstrated 
by  prolonged  boiling,  which 

Fiir.  68.  Muscular  fibres  magnified,  showintf    r        j  xi.  iiu  i 

separate  cells  with  their  nuclei.  hardens     the      tibrcs     and 

facilitates  their  separation.  The  fibrous  rings  are  four  in 
number,  the  rigkt  and  left  auriculo-vejitricular,  the  aortic 
and  pulmonary.  The  former  serve  for  the  attachment  of 
the  muscular  fibres  of  the  auricles  and  ventricles,  and  also 
for  the  tricuspid  and  mitral  valves  ;  the  latter  for  the 
attachment  of  the  arterial  vessels,  semilunar  valves,  and 
muscular  fibres  of  the  ventricles.  The  walls  of  the  left 
ventricle  are  7  lines  in  thickness,  those  of  the  right  about 
2^  lines  ;  the  walls  of  the  left  auricle  are  about  1|  lines  in 
thickness,  the  right  1  line. 

The  Fibres  of  the  Auricles. — These  are  divided  into 
two  sets  or  layers,  a  superjicial,  common  to  both,  and  a 
deep  layer,  proper  to  each.  The  superjicial  fibres  run  in  a 
transverse  direction  across  the  bases  of  the  auricles,  and  are 
most  distinct  on  the  anterior  surface.  The  deep  fibres  con- 
sist of  two  sets,  looped  and  annular.  The  looped  fibres 
commence  at  the  ariculo-ventricular  rings  in  front,  pass 


FIBRE.;  OF  THE  VENTRICLES. 


20» 


upwards  over  the  auricle,  and  return  to  the  rings  on  the 
posterior  part.  The  annular  fibres  surround  the  auricles 
in  a  circular  manner,  and  are  continuous  with  the  circular 
fibres  of  the  veins  which  open  into  them. 

The  Fibres  of  the  Ventricles. — These  consist  accord- 
ing to  Pettigrew,  of  seven  layers,  of  which  three  are  external, 
the  fourth  central,  and  three  internal.  In  the  left  ventricle 
the  fibres  of  the  first  or  external  layer,  lun  almost  vertically 
downwards,  inclining  somewhat  fiom  left  to  right,  and  are 
continuous  at  the  apex  with  the  seventh  or  internal  layer, 
which  pass  upwards  reversely  from  left  to  right ;  these 
two,  are  the  only  layers  that  are  inserted  into  the  aiiriculo- 
ventricular  and  aortic  rings.  Those  of  the  second  layer  rnn 
more  obliquely  downwards  from  left  to  right,  and  are  con- 
tinuous at  the  apex  with  the  sixth  layer,  which  pass 
upwards  with  a  corresponding  obliquity  in  the  reversed 
direction.  The  third  layer  is  similar  in  course,  but  still  more 
oblique  in  direction,  and  is  continuous  at  the  apex  with  the 
sixth  layer.  The  fourth  layer  is  horizontal  or  transverse 
(circular),  and  appears  to  be  single.  The  internal  laj'ers  are 
thicker  than  the  external,  so  that  the  fourth  layer  is  nearer 
the  outer,  than  the  inner  surface  of  the  ventricular  wall. 
The  fibres  of  the  external  layer  curve  around  at  the  apex  in 
a  spiral  manner,  and  form  the  whorl  or  vortex,  constitut- 
ing the  entire  thickness  of  the  heart  at  this  point.  From 
the  seventh  layer  are  chiefly  formed  the  musculi  papillares 
and  columnfe  carneae.  The  fibres  of  the  first  four  layers 
pass  across  the  septum  from  one  ventricle  to  the  other; 
this  is  specially  noticeable  at  the  back  where  there  are  some 
transverse  fibres — the  "  hinge-like  "  fibres  of  the  back  of  the 
heart.  The  right  ventricle  is  similarly  formed,  except  that 
the  external  fibres  are  continuous  with  the  internal,  not 
only  at  the  apex,  but  all  along  the  anterior  coronary  groove. 
The  septum  is  formed  of  fibres  from  both  ventricles,  and 
the  left  half  is  twice  the  thickness  of  the  right. 


1 

^ 


206 


CIRCULATION. 


c 


I 

ft;* 


llv 
firo   \' 


The  heart  is  covered  externally  by  a  layer  of  pericardium 
and  lined  internally  by  a  smooth  shining  membrane,  the 
endocardium,  which  is  continuous  with  the  lining  mem- 
brane of  the  arteries  and  veins.  Both  these  membranes  are 
covered  with  flattened  epithelium  (endothelium)  which 
gives  them  a  smooth  and  glistening  appearance.  The  valves 
of  the  heart  are  formed  by  redu{)lications  of  the  lining  mem- 
brane, strengthened  by  connective  and  elastic  fibres,  and  are 
attached  by  their  bases  to  the  tendinous  rings.  The  tri- 
cuspid and  mitral  valves  which  guard  the  right  and  left 
auriculo- ventricular  openings  respectively,  are  also  attached 
by  their  ventricular  surfaces  and  borders  to  the  columnar 
carnece  by  slender  tendinous  chords,  the  chordce  tendinece, 
The  semilunar  valves  which  guard  the  orifices  of  the  aorta 
and  pulmonary  artery,  three  in  number  for  each,  are  placed 
side  by  side  around  the  orifice,  so  as  to  form  three  little 
pouches,  which  lie  flat  when  the  blood  is  passing  out,  but 
immediately  bulge  out  to  prevent  any  return,  the  corpora 
Arantii  closing  in  the  space  between  the  three  segments  in 
the  centre. 

Vessels  and  Nerves. — The  heart  is  supplied  by  the 
anterior  and  posterior  coronary  arteries  ;  the  nerves  are  de- 
rived from  the  superficial  and  deep  cardiac  plexuses,  which 
are  formed  partly  by  the  cranial  nerves,  and  partly  by  the 
sympathetic. 

Action  of  the  Heart. — The  blood  is  propelled  in  its 
course  by  the  alternate  contraction  and  dilatation  of  the 
muscular  walls  of  the  auricles  and  ventricles  of  the  heart. 
The  two  auricles  contract  together,  and  afteiwards  the  two 
ventricles ;  and  in  each  case  the  contraction  is  immediately 
followed  by  a  relaxation.  The  contraction  is  called  systole ; 
the  dilatation,  diastole.  The  auricles  gradaally  fill  with 
blood  flowing  into  them  from  the  veins,  pr.rt  of  which 
passes  at  once  into  the  ventricles.  When  the  auricles  are  dis- 
tended, they  contract  and  force  the  blood  into  the  ventricles, 
completing  their  diastole.     The  latter  immediately  contract, 


rsajgeaSit 


SOUNDS  OF  THE  HEART. 


207 


and  their  contraction,  or  sys/oZe, follows  so  rapidly,  that  it  ap- 
pears as  if  continuous  with  that  of  the  auricles.  The  ven- 
tricles contract  more  slowly  than  the  auricles,  and  empty 
themselves  more  completely  than  the  latter,  which  always 
contain  a  small  quantity  of  blood.  The  contraction  of  the 
ventricles  upon  the  blood,  closes  firmly  the  auriculo- ventri- 
cular valves  and  forces  open  the  semilunar,  and  the  blood  is 
forced  into  the  aorta  and  pulmonary  artery.  The  musculi 
papillarea  by  their  contraction,  and  attachment  through  the 
chorda}  tendinece,  prevent  the  auriculo-ventricular  valves 
from  being  everted  into  the  auricles.  The  closure  of  the 
tricuspid  valve  is  not  always  complete,  especially  if  the 
ventricle  is  too  full,  and  a  small  quantity  of  blood  flows 
back  into  the  right  auricle.  This  has  been  called  the  safety 
valve  acticm  of  this  valve.  The  semilunar  valves,  as  pre- 
viously mentioned,  lie  flat  to  allow  the  blood  to  pass  out 
but  immediately  fill,  bulge  out  and  meet,  so  as  to  pre-' 
vent  its  return. 

During  contraction  the  heart  appears  to  become  longer 
and  narrower,  although,  in  reality,  it  becomes  shorter  and 
narrower.  This  may  be  demonstrated  by  placing  the  heart 
of  a  recently  killed  animal,  as  a  frog  or  rabbit,  on  the  table, 
and  transfixing  the  base  by  means  of  a  large  needle,  and  in- 
serting another  at  the  apex,  so  as  merely  to  touch  it.  Tf 
the  organ  is  then  stimulated  to  contraction  by  pricking  it, 
the  apex  will  be  observed  to  recede  from  the  needle,  while 
the  heart  at  the  same  time  becomes  narrower  and  shorter. 

Sounds  of  the  Heart. — The  action  of  the  heai-t  is  ac- 
companied by  sounds.  These  are  two  in  number ;  the  first 
or  systolic,  and  the  second,  or  diastolic.  They  follow  each 
other  in  quick  succession,  and  are  succeeded  by  a  pause,  or 
period  of  silence,  after  which  the  first  sound  again  recurs. 
The  duration  of  the  first  sound  is  double  that  of  the 
second,  and  equal  to  that  of  the  pause.  Thus,  if  the 
whole  period  be  divided  into  five  parts,  the  first  two  would. 


.4 


c 
c 

MM 

I. 


WIV 
nru 


rr.v 


lis* 

Jk 

•mi ,, 

litm-  . 


208  CIRCULATION. 

1)0  occupied   by  the  first  sound,  the   third  by>  the   second 
jsound,  and  the  fourth  and  fifth  by  the  pause,  thus : 

2  Parts  occupied  by  the  first  sound | 

1  Part  occupied  by  the  second  sound >  Rhythm. 

2  Parts  occupied  by  the  pause ) 

A  very  short  pause  must  also  exist  between  the  first  and 
second  sound,  otherwise  two  distinct  sounds  could  not  be 
heard.  This  order  of  succession  is  called  the  rhythm  of  the 
heart,  which,  in  a  state  of  health,  is  remarkable  for  its  regu^ 
larity.  The  first  sound  of  the  heart  is  a  heavy,  prolonged 
sound,  synchronous  with  the  impulse  of  the  heart,  and  is 
most  distinctly  heard  over  the  apex ;  the  second  is  a  short, 
distinct  sound,  best  heard  over  the  base.  These  sounds 
somewhat  resemble  the  sounds  of  the  words  "come  "  "  up," 
whispered  in  rapid  succession,  the  former  representing  the 
first  sound,  the  latter,  the  second. 

The  Jirst  sound  is  in  all  probability,  a  compound  sound, 
chiefly  produced  by  the  closure  and  vibration  of  the  tricus- 
pid and  mitral  valves,  and  the  collision  of  the  blood  against 
the  walls  of  the  ventricles.  It  is  also  partly  attributed  to 
the  muscular  sound  produced  by  the  contraction  of  the  ven- 
tricles, and  the  impulse  of  the  heart  against  the  walls  of  the 
chest. 

The  second  sound  is  undoubtedly  due  to  the  closure  and 
vibration  of  the  aortic  and  pulmonary  semilunar  valves. 
They  are  forced  back  by  the  recoil  of  the  blood,  as  one  un- 
furls an  umbrella — with  an  audible  click  as  they  tighten. 
This  may  be  demonstrated  by  fastening  one  of  the  valves 
by  means  of  a  hook  or  ligature,  to  the  side  of  the  aortic  and 
pulmonary  arteries  respectively,  in  some  animal,  as  a  calf,  so 
as  to  allow  regurgitation  to  take  place,  when  it  will  be  ob- 
served that  a  bellow's  murmur  takes  the  place  of  the  second 
sound ;  but  as  soon  as  the  valve  is  allowed  to  resume  its 
play,  the  natural  sound  returns.  It  is  thought  by  some 
that  both  sounds  of  the  heart  are  produced  by  the  same 
cause,  viz  :  the  tension  of  the  valves.     Disease  of  the  valves 


IMPULSE  OF  THE  HEART. 


209 


gives  rise  to  niurmurs  which  interfere  with  the  distinctness 
of  the  sounds. 

Impulse  of  the  Heart. — The  impulse  of  the  heart  is 
most  distinctly  felt  in  the  space  between  the  fifth  and  sixth 
ribs,  two  inches  below  and  one  inch  to  the  inner  side  of  the 
left  nii)))le,  and  is  sometimes  called  the  apex  heat.  The 
force  of  the  imj)ulse  varies  in  different  individuals,  and  in 
the  same  individual  at  different  times;  it  is  very  distinct  in 
emaciated  persony,  and  especially  in  hypertrophy  of  the 
heart.  It  is  produced  by  the  contraction  of  the  spiral  mus- 
cular fibres  of  the  ventricles,  which  causes  a  tilting  of  the 
apex  against  the  walls  of  the  chest,  and  also  by  its  change 
of  shape  in  contraction,  during  which  it  becomes  firm  and 
globular,  and  impinges  upon  the  walls  of  the  chest.  In  its 
movement  the  apex  describes  a  spiral  curve  from  left  to 
right,  and  from  behind  forwards.  That  the  impulse  of  the 
lieart  is  not  due  to  the  tendency  of  the  arch  of  the  aorta  to 
straighten  itself  when  distended  with  blood,  and  the  elastic 
recoil  of  the  parts  about  the  base  of  the  heart,  is  shown  by 
the  fact  that  the  tilting  movement  of  the  heart  will  take 
place  even  when  the  apex  has  been  cut  off.  The  impulse  of 
the  heart  corresponds  with  the  pulse  in  the  arteries,  con- 
sequently the  actions  of  the  heart  may  be  counted  by  the 
pulse  at  the  wrist,  or  in  any  of  the  arteries.  The  beat  is 
not  a  simple  shock  as  it  seems  when  felt  by  the  finger,  but 
may  be  shown  by  the  cardiograph  (a  modified  form  of  the 
sphygmograph)  to  be  compounded  of  three  or  four  shocks 
the  strongest  of  which  only,  is  felt  by  the  finger. 

Frequency  and  Force  of  the  Heart's  Action. — In  a 
healthy  adult,  the  pulsp+ions  vary  from  seventy  to  seventy- 
five  per  minute.  Thv.  frequency  of  the  heart's  action 
diminishes  from  the  commencement  to  the  end  of  life,  as 
will  be  seen  from  the  following  table,  which  represents  the 
average  number  of  beats  in  a  minute : — 


t 

■I 

.4 
1 

If 
I 


lii 
4fv 


c 

MM 

I. 


4:. 


210  CIRCULATION. 

Fn  the  fn-tus 150 

Al  l)irlh 130 

In  infancy ; 1 10 

In  ymilli 80 

Adult  ai^c 75 

Old  ajje 65 

Posture  exorcises  a  most  nMnatkable  intlueiice  on  the  fre- 
quency of  tlio  lieait's  action.  It  is  most  frcMineiit  in  the 
erect  posture,  next  to  that,  in  the  sittinj^,  and  least  in  the 
recmnluint  position.  The  pulse  is  also  most  frequent  in  the 
morning,  liecominnj  slower  towards  evening,  and  is  very 
much  diminished  iluriug  the  ni_L;ht.  It  is  more  frequent  in 
those  of  a  sanguine  te>nj)ei'am(Mit,  than  in  the  i)hli!gmatic, 
and  in  females  than  in  males.  Its  action  is  accelerated  after 
a  meal,  and  still  more  so  after  bodily  exertion,  or  mental  ex- 
citement. In  health,  there  is  a  nearly  uniform  relation 
between  the  frecpiency  of  the  heart's  action  and  the  n.'spira- 
tions,  the  proportion  being  about  four  of  the  former  to  one 
of  the  latter. 

A  certain  rate  of  movement  must  be  maintained  in  the 
circulation,  and  the  impediment  produced  by  friction  must 
be  overcome  l)y  the  muscular  force  of  the  lieart;  and,  since 
the  left  ventricle  propels  the  blooil  through  the  whole  sy.s- 
tem,  while  tl^e  right  sends  it  only  to  tlic  lungs,  the  walls  of 
the  former  are  twice  as  thick  as  the  latter,  and  the  force  of 
the  one  is  double  the  force  of  the  other.  The  force  of  the 
heart's  action  may  be  estimated  either  by  ascertaining  the 
heiglit  of  the  column  of  blood  which  its  action  will  suj)port 
f'Haies'  method),  or  by  causing  the  blood  to  act  on  a  colinnn 
of  mercury  (the  method  of  Poiseuille  and  Volkmami.)  Hales 
introduced  a  long  pipe  inti^  the  carotid  ar*^  )ry  of  a  horse» 
and  found  that  the  blood  rose  to  the  height  of  ten  feet. 
From  this  and  other  experiments,  on  the  lower  animals,  he 
concluded  that  the  human  heart  would  sustain  a  column  of 
blood  seven  and  a  half  feet  high,  the  weight  of  which  would 
be  about  4.1  lbs.,  on  the  square  inch.  Poiseuille's  experiments 
were  made  with  a  glass  tube,  bent  so  as  to  form  a  horizontal 


FORCE  OF  THE  HEART. 


211 


the 


(/^)  and  two  porpcndletilav  portions  (re.  c),  tl>o  latter  Ix'iiij,' 
shaped  like  the  letter  IJ  (Fijj.  09),  namod  the  /inuwultfwnHi)- 
meter.     The  horizontal  portion  is  '"'«  "" 

adapted  by  a  tube  to  the  artery, 
and  the  perpeodictdar  branches 
are  partly  filled  with  mercury, 
the  rise  and  fall  of  which  can  be 
ineahured  on  scales  placed  behind 
them,  and  as  the  rise  and  fall  are 
equal,  the  double  of  either  will 
give  the  weight  of  the  cohuun 
which  t  J  force  of  the  stream  is 
able  to  r.  aintain.  The  results 
corresponded  clcsely  witli  Hales' 
estimate,  being  about  4]  lbs. 
Volkmann  passed  a  solution  of 
sodium  carbonate  into  the  hori- 
zontal branch,  to  prevent  the  blood 
from  coaffulatinjj  on  the  sides  of 
the  vessel.  From  his  experiments, 
it  appears  that  the  force  of  the 
stream  is  capable  of  supporting  a 
column  of  mercury  about  eight  inches  in  height,  or  a  column 
of  blood  about  nine  feet.  But  the  force  which  the  walls  of 
the  heart  must  exert  in  order  to  impart  such  a  pressure  to 
the  blood  which  it  propels,  is  equal  to  a  weight  of  about  Hi 
lbs.  A  modification  of  the  haemadynamometer  for  registering 
the  variations  of  the  force  of  the  heart,  or  arterial  tension 
is  called  a  kymograph  (Fig.  70).  The  open  mercurial  colmnn 
supports  a  floating  rod  and  pen  (a),  in  contact  with  a 
revolving  paper  cylinder  moved  at  an  uniform  rate  by  clock- 
work. The  movements  of  the  pen,  caused  by  the  up  and 
down  movements  of  the  column  of  mercury,  are  inscril)ed 
or  registered  on  the  paper  cylinder. 

Influence  of  the  Neuves  on  the  Heart. — The  heart's 
action  is  governed  by  two  sets  of  nerves,  the  cxclto-motor 


1 

i 
if 

i 


c 

I' 


««■" 

tnr 

iin.1 


212 


CIRCULA  TION. 


antl  inhibHorij.  The  ganglia  and  communicating  nervo 
tibre«  wliicli  preside  over  its  action,  are  situated  in  the 
Fijf.  70.  walls  of  the  heart.     They   have 

been  carefully  studied  in  the 
frog,  in  which  there  are  three 
collections  of  ganglia,  i wo  excito- 
niotor — Remack's,  near  the  infer- 
ior vena  cava,  and  Bidder's,  in  the 
left  auriculo- ventricular  septum, 
and  one  inhibitory — Ludwig's  in 
the  interventricular  septum.  The 
heart  receives  its  excito-motor 
influence  through  certain  fibres 
of  the  sympathetic  (inferior  cer- 
vical ganglion  and  cardiac  plex- 
us) from  the  medulla  oblongata, 
and  its  inhibitory  or  restraining 
influence  from  certain  fibres  of 
the  pneumogastric  (superior  car- 
diac). Stimulation  of  the  sympa- 
thetic nerves  supplying  the  heart, 

Menuriiil  kvmofrraph :    (n)  floatiiiL'    ,        ,,  ,  - 

r<Ki  and  pun ;  (/;)  tuho  connected  with  bv  the  galvauic  cuiTcnt,  incrcascs 

iui  alkaline  Hohition  ;  (r)  tube  and  can-      ,         ,  ,  ,.  i.,  ,1 

nia  for  insertic.n  in  an  artery.  the    heart  8  actlOn  ;    While  OU  the 

other  hand,  stimulation  of  the  pneumogastric  nerve  or  its  in- 
ferior cut  end  diminishes  it,  and  if  the  current  is  sufficiently 
trong,  arrests  it  altoge  ther,  in  diastole.  Voluntary  muscle  so 

Fig.  71. 


Before.  Disri.ijji'.  After. 

Tracinjf  .showing  the  effect  of  Htimulation  of  the  pneumogastric  nerve. 

treated  would  induce  tetanus,  but  the  heart  is  completely 
rehixed  ;  it  knows  no  tetanus.  The  natural  stimulus  of  the 
heait's  action  is  the  blood  in  its  cavities,  which  excites  reflex 


ARTERIES. 


213 


action  through  the  ganglia  and  nerves.  The  heart  appears 
to  be  constantly  acting,  but  it  has  also  its  constant  pauses 
or  intervals  of  rest,  so  that  it  differs  from  other  muscles  onl}' 
in  its  shorter  intervals  of  rest.  The  effects  of  temperature 
on  the  heart's  action  are  interesting.  In  cold  blooded 
animals  the  heart's  action  ceases  at  25°  F.  and  again  at  104" 
F. ;  its  frequency  is  increased  from  the  lower  until  the  maxi- 
mum 72°  F.  is  reached,  and  then  it  declines  irregularly.  In 
warm-blooded  animals,  as  the  rabbit,  it  ceases  at  114°  F. 
the  frequency  being  increased  from  the  lower  to  the  maxi- 
mum of  105°  F. 


ARTERIES. 

The  arteries  are  cylindrical  tubes  which  convey  the  blood 
to  the  different  parts  of  the  body.  They  are  found  in  nearly 
every  part  of  the  body,  except  the  hair,  nails,  epidermis, 
cartilage,  cornea,  ard  the  ultimate  elements  of  the  tis- 
sues. They  were  formerly  supposed  to  contain  air,  because 
they  were  found  empty  after  death,  hence  the  name  arteries. 

Structurv. — They  consist  of  three  coai^,external, middle 
and  internal.     The  external  coat  (tunica  ^'^^-  '^^■ 

adventitia)  is  the  thickest  and  consists 
of  areolar  and  elastic  tissue.  In  arteries 
of  medium  size,  this  coat  is  composed  of 
two  distinct layers,an  inner  or  elastic.and 
an  ou  ter  or  areolar.  In  the  large  arteries 
both  these  coats  are  very  thin,  and  in 
very  small  arteries  the  elastic  coat  is  en- 
tirely absent. 

The  middle  coat  is  thinner  than  the 
preceding,   and    consists    of  muscular 

,  ••.i\  \      1      A'     L'  T  ,An  artery    in   wliicli  the 

(nonstriated;  and  elastic  tissue,  disposed    three  coats  are  dissected. 

chiefly  in  the  transverse  direction.  In  the  largest  arteries 
the  muscular  tissue  forms  only  about  one-third  or  one- 
fourth  of  the  thickness  of  the  middle  coat,  while  in  the 


t 

■A 

H 

It 


214 


CIRCULATION. 


c 
I. 

«\ 


C 

rk 

KMT 

re'i 


medium-sized  arteries  it  predominates,  and  in  the  smaller 
it  is  purely  muscular. 

The  internal  is  the  thinnest,  and  consists  of  two  layers, 
the  inner  or  epithelial,  (endothelial)  and  outer  or  elastic. 
The  former  consists  of  a  single  layer  of  tesselated  epithelium, 
with  round  or  oval  nuclei ;  the  latter  is  a  delicate,  trans- 
parent, fenestrated  membrane,  which  in  medium-sized 
arteries  is  strengcbened  by  several  laminae  of  elastic  tissue. 
Fig.  73.  ipj^g  ari'^ries  are  supplied  with  blood-vessels 

like  the  other  organs  of  the  body.  They  are 
caMad  the  "vasa  vasoruTTi."  They  are  derived 
fromsomeof  the  smaller  arterial  branches,  which 
ramify  in  the  loose  areolar  tissue  connecting 
the  artery  with  its  sheath,  and  are  distributed 
to  the  external  and  middle  coats,  probably  also 
to  the  internal.  They  are  also  supplied  with 
plexuses  of  nerves,derivedchiefly  from  the  sym- 
pathetic system,  but  partly  from  the  cerebro- 
spinal. It  is  through  these  that  the  calibre  of 
the  vessels  is  regulated. 

Function  of  Elastic  Tissue  in  Arteries. 
— It  protects  them  from  the  suddenly  exerted 
pressure  to  which  they  are  subjected  at  each 
contraction  of  the  ventricle.  Under  this  force, 
which  might  burst  a  brittle  tube,  their  elastic 
walls  dilate,  and  by  thus  yielding,  break  the 
shock  of  the  force  impelling  the  blood,  and 
exhaust  it  before  they  are  in  danger  of  burst- 
ing from  being  over-stretched.  Again,  by  their  recoil,  which 
occurs  during|the  diastole  of  the  heart,  they  exert  a  pressure 
which  in  some  degree  replaces  the  action  of  the  heart.  This 
pressure  is  equally  diffused  in  every  direction,  and  tends  to 
drive  the  blood  either  onwards,  or  backwards  to  the  heart ; 
but  the  latter  is  prevented  by  the  closure  of  the  aorticvalves; 
hence  they  moderate  the  jetting  movements  given   to  the 


Nonstriated  mus- 
cular fibre  cells  ;(a^ 
developinff  cell ;  (6) 
more  advanced ;  (d, 
e,  /,)  fibre  cells  of 
human  arteries.  ^ 


I ■['  "inifW'  n'l 


FUNCTION  OF  MUSCULAR  TISSUE. 


215 


blood  by  the  systole  of  the  ventricles,  and  also  equalize  the 
current  of  blood  by  maintaining  pressure  upon  the  stream 
during  the  diastole.  In  this  we  cannot  but  admire  the  beau- 
tiful simplicity  and  harmony  in  the  laws  of  nature.  There 
is  no  loss  of  the  force  of  the  ventricles,  for  that  part  of  their 
force  which  is  expended  in  dilating  the  arteries  is  restored 
in  full,  according  to  the  law  of  action  of  elastic  bodies,  by 
which  they  return  to  the  state  of  rest  with  a  force  equal  to 
that  by  which  they  were  moved.  The  elasticity  of  the  ar- 
teries also  giv(5s  them  a  capacity  for  receiving,  under  certain 
circumstances,  more  than  the  average  quantity  of  blood, 
and  it  enables  them  to  adapt  themselves  to  the  various 
movements  of  the  different  parts  of  the  body.  In  conse- 
quence of  their  elasticity,  the  arteries  are  not  only  dilated, 
but  also  I  ^ated.  This  is  most  apparent  in  arteries  which 
are  curveu. 

Function  of  Muscular  Tissue  in  Arteries.  —  When 
an  artery  is  cut  across,  its  divided  ends  contract,  and  the 
orifices  may  be  partially  or  completely  closed,  owing  to  the 
contraction  of  the  muscular  tissue.  This  contraction  is 
greater  in  the  young  than  in  the  aged,  and  in  animals 
than  in  man,  and  continues  many  hours  after  death.  It  is 
also  increased  by  the  application  of  cold,  styptics,  galvanism, 
irritation,  or  by  torsion  or  twisting  the  cut  ends  of  the  ar- 
tery. Owing  to  their  contraction  after  death,  the  vessels 
cannot  be  injected  until  the  rigor^mortis  passes  off.  The 
muscular  tissue  of  the  arteries  can  assist  only  in  a  very 
small  degree,  in  propelling  the  onward  current  of  the  blood. 
The  manner  in  which  the  arterial  trunks  taper  towards 
their  distal  extremities,  renders  it  mechanically  impossible 
that  the  strong  contraction  of  circular  fibres  would  drive 
the  blood  onward  ;  in  fact,  thejtendency  would  be  in  the  op- 
posite direction.  The  principal  use  of  the  muscular  tissue 
is  to  regulate  the  supply  to  different  parts  of  the  body,  ac- 
cording to  the  activity  of  the  function  of  each  part  at  differ- 
ent times ;  for  example,  the  brain  does  not  require  so  much 


t 
f 

M 

1 


21 G 


CIRCULATION. 


C. 

I 

WW 


^ 


c 

»»» 
(St 


blood  (Inrinfif  aleop  as  during  mental  labor ;  tlio  stomacli 
does  not  rociuiro  so  much  blood  during  ('a.sting,  as  during  di- 
gostion,  etc.  Tlio  heart  cannot  regulate  the  supjdy  to  each 
part  at  particular  periods;  but  it  may  bo  regulate<l  by  the 
contraction  of  the  muscular  coat  o"  the  arteries,  or  it.s 
passive  dilatation,  so  as  to  diminwh  or  increase  the-supply  of 
blood  according  to  the  demand.  The  muscular  tissue  also 
assists  the  elastic  in  adaptlvij  the  vessels  to  the  quantity  of 
blood  they  nuiy  contain,  g'w'm^  uniforimfij  to  the  amount  of 
pressure  exercised  on  the  blood,  and  niaintaining  the  tone  of 
the  blood-vessels.  Agaiu,  the  contraction  of  tho  muscular 
coat  of  a  wounded  artery,  first  limits,  and  then  arrests  the 
escape  of  the  blood  when  assisted  by  the  formation  of  fibrin 
in  the  moiith  of  the  wounded  vessel.  This  is  nature's  mode 
of  arresting  hemorrhage  (natin-al  hemostasis).  The  contrac- 
tion of  the  arteries  is  determined  chiefly  by  the  influence  of 
the  great  s\nnpathetic  system. 

Function  OF  Tiir^  Arteries. —  From  what  has  been 
already  stated,  wo  may  infer  that  the  function  of  the 
arteries  is — -first,  to  convey  and  distribute  the  blood  to  the 
different  parts  of  tlio  body  ;  second,  to  equalize  the  current, 
and  moderate  the  jetting  movements  given  to  the  blood  by 
the  ventricles ;  third,  to  regulate  tho  supply  to  tho  differ- 
ent parts  of  the  organism  according  to  the  demand. 

Anastomosis  of  Arteries. — The  arteries  have  a  re- 
markable tendency  to  comnuinicate  with  each  other  in  their 
course,  in  order  more  fully  to  supply  the  organs  to  which 
they  are  distributed.  This  is  called  an  anastomosis.  One 
of  the  simplest  modes  is  the  union  of  two  arteries  to  form 
one,  as  the  union  of  the  vertebrals  to  form  tho  basilar.  An- 
other mode  is,  the  union  of  two  branches  to  form  an  arch 
from  the  convexity  of  which  other  branches  are  given  off, 
■which  may  in  their  turn  form  arches,  and  this  may  be  re- 
peated until  the  resulting  branches  are  reduced  to  a  very 
small  size,  when  they  terminate  in  tho  capillaries,  as  for  ex- 
ample, the  mesenteric  arteries,     A  third  mode,  which  is  the 


wm 


PULSE. 


217 


lach 


most  remarkable,  is  tlie  communication  of  two  adjacent  ves- 
sels by  a  distinct  vessel  passing  from  one  to  the  other,  as  in 
the  chrle,  of  WUHh.  Hero  the  antcsrior  cerebral  arteries  are 
united  by  a  short  cross  branch — the  anterior  communicating, 
and  the  carotid  on  each  side  is  united  to  the  posterior  cere- 
bral by  the  posterior  communicating.  [n  this  way  the 
brain  is  protected  in  all  its  parts  against  loss  of  blood,  if  the 
circulation  in  any  of  the  main  channels  should  b<5  arrested. 

The  most  common  form  is  found  in  the  limi)s,  where  the 
main  trunk  usually  divides  into  two  branches,  from  which 
smalhir  branches  are  given  off',  which  communicate  with 
each  other  at  various  points,  especially  around  the  joints. 
These  branches  also  conununicate  with  (others  from  adja- 
cent aiteries,  as  for  e.xami)le,  the  deep  femoral  with  the 
sciatic,  etc.  By  such  an  arrangement,  the  ])ro|)er  nutrition 
of  the  limb  is  securtMl  by  collateral  circulation  in  the  event 
of  the  main  trunk  being  ligatured,  or  otherwise  occluded. 
In  the  application  of  a  ligatuie,  the  surgecm  should  always 
make  allowance  for  the  anastomoses  in  the  vicinity  of  the 
wound.  In  consequence  of  the  free  anastomoses  between 
the  adjacent  branches,  it  is  always  necessary  when  a  large 
artery  is  wounded,  to  apply  a  ligature  both  above  and  be- 
low the  wound,  in  order  to  prevent  the  occurrence  of  subse- 
quent hemorrhage. 

Pulse. — When  the  finger  is  applied  to  the  wrist,  or  any 
of  the  arteries  of  the  body,  it  is  felt  to  beat  or  ])ulsate  in 
correspondence  with  the  systole  of  the  heart.  The  sensa- 
tion communicated  to  the  finger  is  due  to  the  dilatation  and 
elongation  of  the  part,  caused  by  the  jetting  movements  of 
the  current  of  blood  in  the  vessel.  Each  jet  of  blood  cr3ates 
a  wave,  which  moves  along  the  whole  arterial  system.  It 
is  not  supposed  that  the  jet  of  blood  from  the  ventricle  im- 
parts its  pressure  on  the  blood  contained  in  the  arteries  so 
as  to  dilate  the  whole  arterial  system  at  once  ;  but  it  dis- 
places or  propels  the  blood,  and  flows  on  by  what  may  be 
called  a  head-iuave.     A  certain  time  will  be  required  for  the 


^^1 


218 


CIRCULATION. 


c 
1. 


HIV 


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CM 


wave  to  travel  from  the  heart  to  distant  arteries,  so  that 
although  the  wave  corresponds  with  the  systole  of  tlie  heart 
yet  it  is  not  in  exact  synchronism  with  it,  the  difference 
varying  according  to  tlie  distance  from  the  heart.  The 
longest  interval  is  about  one-sixth  to  one-eighth  of  a  second. 
T  -  rapidity  of  the  wave  is  about  28i  feet  per  second,  or 
20  to  30  times  as  great  as  the  velocity  of  the  stream. 

Fig.  74. 


SphyKinograph  applied  to  tlie  Ann. 

An  instrument  for  delineating  the  character  of  the  pulse 
is  termed  the  Sfhygmogra'ph.  It  is  made  fiist  to  the  arm 
and  the  movements  of .%  small  button,  which  takes  the  place 
of  the  finger,  are  communicated  by  means  of  a  lever,  and 
registered  by  tracings  in  ink  upon  a  card  moved  by  clock- 
work (Fig.  74),  In  a  healthy  pulse  the  up-stroke  or  'per- 
cussion iTYiimlse  is  nearly  vertical,  while  the  down-stroke 
is  ver}'^  oblique,  and  presents  a  slight  notch  or  re-ascent ; 
the  more  deficient  in  tone  the  pulse,  the  more  distinct  is  the 
notch  in  the  down  stroke,  and  vice  versa.  In  some  instances, 
the  re-ascent  is  so  marked  as  to  be  perceptible  to  the  finger, 
and  is  called  a  dicrotic  pulse. 

HhQ  character  of  the  pulse  will  depend — First,  upon  the 
force  of  the  heart  ;  second,  upon  the  integrity  of  its  valves 
and  orifices ;  third,  upon  the  quantity  and  quality  of  the 
blood  in  the  system ;  and  fourth,  upon  the  condition  of  the 
walls  of  the  arteries,  whether  rigid  or  yielding,  tense  or 
flabby,  etc.  The  qualities  of  softness  or  fulness,  or  wiry- 
ness,  of  compressibility  or  incompressibility,  etc.,  which  are 
familiar  to  the  practical  physician,  are  determined  by  the 
yielding  or  the  resisting  condition  of  the  arterial  walls. 


VEINS. 


219 


Influence  of  the  Nekves  on  the  Arteries.  —  The 
arteries  in  all  parts  of  the  body  receive  nerve  filaments  from 
the  sympathetic,  called  vcLsomotor  branches.  These  give 
tone  to  the  muscular  fibres  of  the  arteries,  and  if  stimulated, 
as  e.g.,  by  an  electric  current,  the  arteries  contract  and 
diminish  the  supply  of  blood  to  the  parts  ;  if  divided,  the 
arteries  are  paralyzed  and  become  dilated.  The  vasomotor 
nerves  come  primarily  from  the  gray  matter  of  the 
medulla  oblongata,  but  communicate  with  the  various  gan- 
glia of  the  sympathetic.  The  medulla  is  called  the  "  vaso- 
motor centre,"  and  the  ganglia  of  the  sympathetic,  "second- 
ary centres."  The  reflex  impressions  received  by  these  centres 
rnay  either  result  in  contraction  or  dilatation  of  the  vessels. 
If  the  impression  received  through  the  sensory  nerve  of  a 
part  is  sufficiently  strong,  it  leads  to  contraction  of  all  the 
blood-vessels  of  the  body,  except  those  in  the  part  from 
which  the  impression  was  received  which  become  dilated. 
The  former  action  is  called  excitomotor,  the  latter  inhibitory. 
The  redness  which  follows  the  irritation  of  the  skin  is  a 
good  example. 

VEINS. 

The  veins  return  the  blood  from  the  various  tissues  and 
organs,  to  the  right  side  of  the  heart.  They  are  more 
numerous,  and,  with  the  exception  of  the  pulmonic  veins, 
more  capacious  than  the  arteries.  They  commence  in  the 
capillaries,  and  uniting  form  trunks,  some  of  which  are 
superficial,  andothere  deep,  accompanying  their  correspond- 
ing arteries. 

Structure. — In  structure  they  consist  of  three  coats, 
which  resemble  the  arteries,  except  that  the  outer  coat  is 
thicker  and  contains  some  muscular  tissue,  and  the  middle 
coat  is  thinner.  Muscular  tisuie  is,  however,  entirely  absent 
in  the  sinuses  of  the  dura  mater,  uterus,  and  corpora  caver- 
nosa, cerebral  veins,  retinal  veins,  and  the  veins  of  the  can- 
cellous tissue  of  bones.     Most  veins  have  valves  which  pre- 

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CIRCULATION. 


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vent  the  reflux  of  the  blood.  They  are  more  numerous  in 
the  Ruperficial  than  in  the  deep  veins,  and  in  those  of  the 
lower  than  the  upper  extremity.  The  valves  are  formed 
by  reduplications  of  the  lining  membraue,  serpilunar  in  form, 
and  are  attached  by  their  convex  margins  to  the  walls  of  trie 
veins.  They  are  generally  arranged  in  pairs,occasionally  there 
are  three,  but  sometimes  only  one.  In  very  small  veins  they 
are  absent ;  also  in  the  venje  cavae,  pulmonary  veins,  hepatic 
veins,  portal  vein,  renal,  uterine,  ovarian,  cerebral  and 
spinal  veins,  veins  of  the  cancelli  of  bones,  and  in  the 
umbilical  vein.  The  veins  are  supplied,  like  the  arteries, 
by  little  vessels  (vasa  vasorum) ;  but  the  nerves  are  not  so 
easily  detected  upon  them. 

Circulation  in  the  Veins. — In  the  veins,  the  blood 
moves  in  a  continuous  stream,  and  the  velocity  of  the 
venous  current  is  considerably  less  than  the  arterial. 
The  circulation  is  produced  by  the  vis  a  tergo  of  the  heart, 
the  action  of  the  capillaries,  the  contraction  of  the  volun- 
tary  muaclea,  and  the  inspiratory  movements  of  th£  thorax. 

The  vis  a  tergo  of  the  heart  may  produce,  in  certain  con- 
ditions of  the  system,  a  distinct  venous  pulse,  corresponding 
with  the  impulse  of  the  heart,  the  wave  having  passed 
through  the  capillaries.  This  may  be  called  the  com- 
"municated  or  systolic  venous  pulse,  and  must  be  carefully 
distinguished  from  the  regurgitant  venous  pulse,  which  is 
caused  by  the  regurgitation  which  takes  place,  in  some  per- 
sons, into  the  venous  trunks,  during  the  systole  of  the  right 
auricle.  In  health,  the  regurgitation  is  very  small  and  in- 
distinct ;  but  when  the  right  cavities  of  the  heart  are  dilated, 
a  lai'ge  quantity  of  blood  is  regurgitated,  and  a  distinct  venous 
pulse  is  visible  in  the  superficial  and  deep  veins  of  the 
neck. 

The  inspiratory  movements  of  the  thorax,  by  enlarging 
the  capacity  of  the  chest,  tend  to  create  a  vacuum,  which  is 
<jhiefly  filled  by  the  rush  of  air  into  the  chest,  but  partly 
by  the  afflux  of  blood,  which  must  be   principally  venous, 


"'•iiltiLt-  - 


VEINS. 


221 


since  the  closure  of  the  aortic  valves  would  oppose  any 
reflux  in  the  aorta.  This  may  be  demonstrated  by  intro- 
ducing a  bent  glass  tube  into  the  jugular  vein  of  an  animal, 
the  vein  being  tied  above  the  point  where  the  tube  is  in- 
serted, and  the  other  end  immersed  in  some  colored  fluid. 
It  will  be  uuscrv«^d  that  at  each  inspiration  the  colored  fluid 
will  ascend  in  the  tube,  while  nuring  expiration  it  will 
either  remain  stationary  or  sink.  Or  it  may  be  shown  by 
the  hmmadynamometer.  The  effect  of  inspiration  on 
the  veins  is  only  observable  in  the  larger  ones.  Forced 
expiratory  movements  on  the  other  hand,  retard  venous 
circulation,  as  may  be  seen  by  holding  the  breath  for  a  few 
seconds,  or  by  straining,  when  the  veins  about  the  neck  and 
face  swell  up  and  become  distended,  but  immediately 
return  to  their  former  size  when  breathing  is  restored.  In 
surgical  operations  in  the  region  of  the  neck,  the  wounding 
of  an  enlarged  vein  which  r-^mains  patulous,  is  liable  to  be 
followed  by  the  entrance  of  air  into  the  circulation  during 
a  deep  inspiration,  and  sudden  death  is  the  result. 

The  contraction  of  the  voluntary  muscles  has  a  most 
marked  effect  in  favouring  the  circulation  of  the  blood  in 
the  veins,  as  may  be  seen  in  cases  of  venesection,  when  the 
patient  is  directed  to  move  his  fingers  freely.  During 
muscular  action  a  portion  of  the  veins  is  compressed,  and  as 
the  blood  is  prevented,  by  the  valves  in  the  veins,  from  pass- 
ing backwards  in  the  small  vessels,  it  is  necessarily  forced 
onwards  towards  the  heart.  As  the  muscles  are  relaxed 
the  veins  again  swell  out,  to  be  re-compressed  by  the 
renewal  of  the  muscular  force,  and  so  on.  This  force  is  an 
important  agent  in  maintaining  the  circulation,  since  the 
voluntary  muscles  are  more  or  less  active  in  nearly  every 
position  of  the  body,  and  the  veins  liable  to  be  compressed 
by  them. 

The  contraction  of  the  muscular  tissue  of  the  walls  of 
tlie  veins  also  exerts  considerable  influence  in  the  circula- 
tion of  the  blood  in  the  veins. 


1 
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222 


CIRCULATION. 


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CAPILLARIES. 

Tlio  capillaries  are  the  connecting  link  between  the 
arteries  and  veins,  and  are  found  in  all  parts  of  the  body 
except  the  uterine  placenta,  copora  cavernosa  of  the  penis, 
hair,  nails,  epidermis,  etc.  In  structure  they  appear 
under  the  microscope,  to  consist  of  a  homogeneous,  finely 
tibrillated  membrane,  with  cell  nuclei  which  adhere  to  or 
*"'«•  ^*-  are  embedded  in  it,  at  certain  dis- 

tances apart.  This  is  lined  inter- 
nally by  a  layer  of  transparent, 
elongated  and  flattened  nucleated 
cells  (endothelium).  At  the  point 
of  junction  of  some  of  the  endo- 
thelial cells,  small  openings  or 
stomaLa  (Fig,  7^,  c)  may  be  seen 
resembling  those  of  serous  mem- 
branes (i),101),  through  which  the 
white  corpuscles  make  an  active 
exit,  and  the  red  ones  are  some- 
n^;,S7Zl  rf  o^e'wltir uo£  tiuics  passivcly  forced  out.  These 
S  u^  S.;  'ori;lv27.=!  appearances  are  readily  seen  after 
^^■l^'Zn^''^"^'''''''^'"  staining  with  solution  of  silver 
nitrate.  The  capillaries  vary  in  diameter  in  the  dif- 
ferent tissues,  the  average  being  about  s-^-^  of  an  inch, 
(8.3  mmm)  and  their  length  is  about  3\j  of  an  inch  (.8  mm). 
The  smallest  are  those  of  the  brain  and  mucous  membrane 
of  the  intestines ;  the  largest  are  those  of  the  skin  and 
medulla  of  bones.  They  form  meshes,  which  vary  in  different 
tissues  ;  for  example,  they  are  rounded  in  the  lungs,  elon- 
gated in  the  muscles  and  nerves,  and  looped  in  the  papillae 
of  the  tongue  and  skin.  The  closest  network  is  found  in 
the  lungs,  and  choroid  coat  of  the  eye.  In  the  lungs,  the 
interspaces  are  smaller  than  the  capillaries  themselves. 
The  network  is  also  very  fine  in  the  iris,  ciliary  body,  and 
liver.     As  a  rule  the  more  active  the  function  of  an  organ, 


CIRCULATION  IN  THE  CAPILLARIES. 


223 


the  closer  is  the  capillary  network,  and  the  larger  its  supply 
of  blood.  In  the  compound  tissues  the  capillaries  do  not 
ramify  among  the  ultimate  particles  of  the  tissues ;  thus 
in  muscle  the  vessels  lie  between  the  fibres,  but  do  not 
pierce  the  sarcolemma.  In  nerves,  in  the  same  way,  they 
are  separated  from  the  nervous  matter  by  the  tubular 
membrane.  In  mucous  and  serous  membranes  they  are 
imbedded  in  the  sub-areolar  tissue,  which  forms  a  nidus  for 
them. 

Circulation  in  the  Capillaries.  —  The  current  of 
blood  flows  through  the  capillaries  with  a  constant  equable 
motion,  as  may  be  seen  under  the  micioscope  in  the  frog's 
foot  or  bat's  wing.  In  the  central  part  of  the  current  in  the 
larger  vessels  may  be  seen  the  red  corpuscles  moving  with 
considerable    rapid-  Fig.  76. 

ity;  while  near  the 
edges  of  the  vessel 
there  is  a  transpar- 
ent stratum  of  clear 
plasma,  in  which 
may  be  seen  some 
white  corpuscles  mo- 
ving ver}'  .slowly. 
The  stream  at  the 
circumference  is  very 
sluggish,  almost  mo- 
tionless, and  is  call- 

1    11         j'Tj  T  T  ijapiiiary  piexus '.n  rne  irogs  loot,  x  iiu;    i,  trunK  or 

ed  the  still  layer .  lU  vein;  2,  its  branches;  3,  piKment  cells.    (Warner.) 

the  smaller  vessels  the  corpuscles  pass  along  in 
single  file  and  sometimes  become  bent  and  other- 
wise distorted  in  order  to  acommodate  themselves 
to  the  curvatures  of  the  capillaries.  Whenever  the 
current  is  obstructed  or  retarded  in  any  way,  the  white 
corpuscles  accumulate  in  the  affected  part,  and  become  more 
numerous  in  proportion  to  the  red.  The  circulation  of  the 
blood  In  the  capillaries  is  partly  due  to  the  vis  a   tergo   of 


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224 


CIRCULATION. 


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<^«  ^«ar<,  and  rccoii  of  the  arteries,  and  partly  also  to  the 
attractive  or  selective  power  of  the  tissues.  Tho  former  has 
been  alroatly  referred  to,  in  connection  with  tho  heart  and 
arterioa.  With  regard  to  the  latter,  it  is  in  the  capillaries 
that  those  chemical  and  physical  changes  between  the 
blood  and  tho  tissues  take  place,  in  which  tho  phenomena 
of  nutrition  essentially  consist.  A  certain  force  is  generated 
by  this  interchange,  which  promotes  tho  circulation  of  tho 
blood  through  the  capillaries.  It  is  termed  the  attractive 
or  selective  pow&r  of  tho  tissues,  or  by  Carpenter  capillary 
power.  It  may  be  explained  as  follows : — As  the  blood 
charged  with  oxygen  and  nutritious  substances  for  the  sup- 
ply of  tho  tissues  approaches  the  capillaries,  a  rapid  imbibi- 
tion takes  place  with  such  energy,  that  it  pushes  before  it 
into  the  veins,  the  blood  from  which  tho  nutritious  ele- 
ments had  been  previously  removed,  and  which  also  con- 
tains tho  effete  matter.  This  force  resembles  that  by  which 
tho  circulation  is  maintained  in  plftQts,  and  in  some  of  the 
lower  order  of  animals. 

The  capillaries  are  surrounded  by  a  plexus  of  nerves, 
similar  to  that  of  the  larger  vessels,  'f  heir  contraction  during 
anger  and  from  fear,  and  their  dilatation  during  blushing, 
can  only  be  referred  to  the  influenoe  of  the  nerves,  for  in 
these  cases  the  changes  are  so  rapid  that  the  heart  has  not 
tim<)  to  eit'ect  them.  Under  one  kind  of  nervous  emotion 
the  vessels  contract,  and  empty  themselves,  and  tlie  coun- 
tena.:c°  becomeo  deadly  pale,  as  in  anger,  fear,  etc.  Under 
another  kind  of  nervous  emotion  the  vessels  dilate,  become 
filled  with  blood,  and  the  cheek  is  suffused,  as  in  blushing. 

The  heart's  action  alone  is  sufficient  to  carry  on  the  cir- 
culation of  the  blood,  but  it  is  aided  by  other  forces  which 
are  supplementary.  The  combined  forces  by  which  the 
blood  is  propelled  throughout  the  body,  are,  first  and 
chiefly,  the  muscular  force  of  the  heart ;  second,  the  recoil 
of  the  elastic  walls  of  the  arteries ;  third,  the  attractive  or 
selective  power  of  the  tissues ;  fourth,  the  pressure  of  the 


VELOCITY  OF  THE  CIRCULATION. 


925 


muscles  among  which  some  of  the  veins  lie  ;  fifth,  the  aetioA 
of  the  muscular  tissue  in  the  coats  of  the  veins  ;  and  sixth, 
the  inspiratory  movements  of  the  chest. 


VELOCITY   OF  THE  CIKCULATION. 

The  velocity  of  the  current  of  blood  at  any  given  point 
in  the  system,  is  inversely  proportional  to  the  sectional 
area  at  that  point.  The  united  area  of  the  capillaries  i» 
400  times  as  great  as  that  of  the  aorta,  and  hence  the 
velocity  of  the  blood  in  the  capillaries  is  about  f^^  of  that 
in  the  aorta. 

Velocity  in  the  Arteries. — The  velocity  of  the  circu- 
lation in  the  arteries,  may  be  ascertained  by  an  instrument 
similar  to  tliat  used  for  measuring  the  force  of  the  heart. 
It  is  greater  than  in  any  other  pari  of  the  system. 
Volkmann  estimates  the  velocity  with  which  the  blood 
moves  in  the  carotid  artery,  at  about  twelve  inches  'per 
second.  It  diminishes  during  the  diastole  of  the  ventriclea 
and  in  arteries  remote  from  the  heart,  as  the  metatarsal,  in 
which  it  is  2.2  inches  per  second. 

Velocity  in  the  Veins. — The  velocity  of  the  venous- 
current  is  to  that  of  the  arterial  ^ ;  two  to  three,  or  about 
eight  inches  per  second,  as  nearly  as  can  be  ascertained. 

Velocity  in  the  Capillaries. — The  rate  of  movement 
of  the  blood  in  the  capillaries  may  be  determined  by  the 
microscope.  It  is  slower  than  in  either  the  arteries  or 
veins,  being  on  an  average,  about  ,V  of  an  inch  per  second. 

Velocity  in  the  Body. — It  is  estimated  that  the 
ventricles  and  auricles  are  each  capable  of  holding  about 
three  ounces  of  blood,  and  that  this  quantity  is  propelled 
by  either  ventricle  at  each  systole,  and  that  the  whole 
amount  of  blood  in  the  system  is  about  eighteen  pounds. 
This  would  require  ninety-six  pulsations  for  its  passage 
through  either  side  of  the  heart,  and  allowing  seventy-two 
pulsations  to  a  minute,  the  time  occupied  in  transmitting 


% 

It 

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i 


226 


CIRCULATION. 


c 
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I. 

»•• 

an 


the  whole  would  be  1^  minutes.  But  it  has  been  ascer- 
tained by  experiments  on  animals,  as  the  horse,  that  sub- 
stances in  solution,  such  as  potassium  ferrocyanide,  barium 
nitrate,  etc.,  may  be  detected  in  the  blood  drawn  from  the 
carotid  artery  within  twenty  seconds  after  it  has  been 
introduced  into  the  jugular  vein  of  the  opposite  side.  In 
the  dog,  the  heart's  action  may  be  arrested  in  eleven  or 
twelve  seconds,  by  the  introduction  of  a  solution  of  potas- 
sium nitrate  in  the  jugular  vein ;  in  the  rabbit  in  about 
four  seconds,  and  in  fowls  in  about  six.  The  introduction 
of  such  poisons  as  hydrocyanic  acid  and  strychnine,  are 
equally  rapid  in  their  effects.  Hence,  it  appears  that  the 
rapidity  of  the  circulation  is  underrated  in  the  estimate 
founded  upon  the  capacity  of  the  heart,  and  the  number  of 
pulsations  in  a  minute.  It  has  been  estimated  by  Volk- 
mann,  that  in  man  the  whole  circuit  is  completed  in  con- 
siderably less  than  one  minute. 

Peculiarities  of  the  Circulation. — These  are  observed 
in  the  lungs,  liver,  brain,  spleen  and  erectile  organs.  The 
chief  peculiarity  in  the  pulmonic  circulation  is,  that  the 
artery  carries  venous  blood  to  the  lungs,  and  the  veins 
return  arterial.  The  portal  circulation  is  peculiar  in  being 
a  kind  of  offset  from  the  general  circulation.  The  peculiarity 
of  the  circulation  in  the  brain  is,  that  it  is  provided  with  a 
uniform  supply  of  blood.  Thi^3  is  secured  by  thf  number 
and  tortuosity  of  the  vessels,  and  their  large  anastomoses 
in  the  formation  of  the  circle  of  Willis.  The  occurrence 
of  large  venous  trunks  or  indistensible  sinuses  within  the 
cranium,  is  also  peculiar.  It  is  also  stated  by  Dr.  Kellie, 
that  in  bleeding  animals  to  death,  the  brain  does  not 
become  exsanguine,  owing  to  atmospheric  pressure,  unless 
an  opening  be  made  in  the  cranium.  But  this  is  disputed 
by  Dr.  Burrows,  who  concludes,  from  careful  experiments, 
that  the  brain  may  become  exsanguine  without  any 
apparent  aperture  in  the  cranium,  and  that,  in  health,  slight 
variations  maj"^  occur  in  the  quantity  of  blood  sent  to  the 


FCETAL  CIRCULATION. 


227 


brain.  In  the  spleen,  the  most  striking  peculiarity  is  thai 
each  of  the  larger  branches  supplies  chiefly  that  part  of 
the  organ  to  which  it  is  distributed,  having  no  anastomosis 
with  the  adjoining  branches. 

The  erectile  tissues  are  the  penis,  clitoris,  erectile 
tissijbes  of  the  vagina,  and  the  nipple  in  both  sexes.  The 
venous  plexuses  of  the  erectile  tissue  become  filled  with 
blood,  which  swells  and  distends  the  organ,  causing  it  to 
assume  an  erect  condition.  This  influx  of  blood  may  be 
caused  by  local  irritation,  or  by  certain  emotions  of  the 
mind  communicated  through  the  great  sympathetic  system. 
Erectile  tissue  consists  of  a  plexus  of  veins  with  varicose 
enlargements  enclosed  in  a  fibrous  envelope,  with  trabecular 
partitions.  There  are  also  some  nonstriated  muscular 
fibres,  which  are  connected  in  some  way  with  the  process 
of  erection.  They  may  either  by  their  contraction  prevent 
the  due  return  of  blood  from  the  parts,  or  by  their  relax- 
ation allow  the  plexuses'to  fill  with  blood,  and  remain  so 
until  the  stimulus  to  erection  subsides,  when  they  contract 
and  gradually  expel  the  excess  of  blood. 

FcETAL  Circulation. — In  the  foetus,  the  course  of  the 
circulation  is  modified  in  consequence  of  the  inaction  of  the 
lungs.  The  aeration  of  the  blood  is  efi'ected  b}'  the  placenta, 
through  which  also  the  foetus  is  nourished,  so  that  the 
placenta  serves  the  double  purpose  of  a  respiratory  and 
nutritive  organ,  or  in  other  words,  it  performs  the  office  of 
the  lungs  and  stomach  in  the  foetus.  The  course  of  the 
circulation  in  the  foetus  is  as  follows : — The  arterial  blood 
is  carried  from  the  placenta  to  the  foetus,  along  the  umbilical 
cord,  by  the  umbilical  vein.  It  then  entei-s  the  umbilicus, 
and  passes  upwards  along  the  free  margin  of  the  longitu- 
dinal ligament  of  the  liver  to  its  under  surface,  where  it 
gives  oft'  two  or  three  branches  to  the  left  lobe,  and  others 
to  the  lobus  quadratus  and  Spigelii.  At  the  transverse 
fissure  it  divides  into  two  branches ;  the  larger  is  joined 
by  the  portal  vein  and  enters  the  right  lobe ;  the  smaller 


1 

■I 


II! 


228 


CIRCULATION. 


c 

MM- 
t\ 
I. 

I- 

iri 

MV 

an 

c 

f»..v 

& 


WW 


paseeH  onwards,  under  the  name  of  the  ductus  venosus, 
which  joins  the  left  hepatic  vein,  where  the  latter  empties 
into  the  inferior  vena  cava.  Hence  the  blood  reaches  the 
vena  cava  in  three  different  ways  ;  most  of  it  passes  through 
the  liver  with  the  portal  venous  blood,  and  is  returned  to 
the  vena  cava  by  the  hepatic  veins ;  some  passes  through 
the  liver  directly,  to  be  returned  also  by  the  hepatic  veins ; 
and  the  smallest  quantity  is  carried  on  b}'  the  ductus 
venosus  to  the  vena  cava.  In  the  inferior  vena  cava,  the 
blood  is  joined  by  that  which  is  being  returned  from  the 
lower  extremities  and  viscera  of  the  abdomen ;  it  then 
enters  the  right  auricle,  and  guided  by  the  Eustachian  valvo 
passes  through  the  foramen  ovale  into  the  left  auricle, 
where  it  is  mixed  with  a  small  quantity  returning  from  the 
lungs.  From  the  left  auricle  it  passes  into  the  left  ventricle, 
from  the  left  ventricle  into  the  aorta,  to  be  distributed 
chiefly  to  the  head  and  upper  extremities — a  small  quantity 
passing  into  the  descending  aorta.  From  the  head  and 
upper  extremities  the  blood  is  returned  by  the  superior 
vena  cava  to  the  right  auricle,  where  it  is  mixed  with  some 
from  the  inferior  vena  cava.  It  then  passes  into  the  right 
ventricle,  and  from  the  right  ventricle  into  the  pulmonary 
artery,  but  the  lungs  of  the  foetus  being  almost  impervious, 
only  a  small  quantity  is  distributed  to  them  by  the  pul- 
monary arteries,  and  is  returned  to  the  left  auricle  by  the 
pulmonary  veins ;  the  greater  part  of  the  blood  from  the 
right  ventricle  passes  through  the  ductus  arteriosus  into 
the  descending  aorta,  where  it  is  mixed  with  a  small 
quantity  of  blood  transmitted  by  the  left  ventricle  into  the 
aorta.  It  then  descends  along  this  vessel  to  supply  the 
viscera  of  the  abdomen,  pelvis,  and  lower  extremities-^ 
the  greater  portion,  however,  being  conveyed  by  the 
umbilical  arteries  to  the  placenta. 

When  the  child  is  born,  and  respiration  established,  an 
increased  amount  of  blood  is  sent  to  the  lungs,  and  the 
placental  circulation  is  cut  off.     The  foramen  ovale  gradu* 


FCETAL  CIRCULATION. 


229 


ally  closes  up,  being  completed  about  the  tenth  day.  The 
ductus  arteriosus  contracts  as  soon  as  respiration  is  estab- 
lished, and  is  completely  closed  from  the  fourth  to  the 
tenth  day.  The  umbilical  arteries,  between  the  umbilicus 
and  the  fundus  of  the  bladder,  become  obliterated  between 
the  second  and  fitth  days.  The  umbilical  vein  and  ductus 
venosus  also  become  obliterated  between  the  second  and 
fifth  days.  In  some  instances  the  foramen  ovale  does  not 
close  readily,  and  the  blood  continues  to  pass  through  into 
the  left  auricle  after  birth,  giving  rise  to  a  bluish  color  of 
the  surface  of  the  body.  This  condition  is  called  cyanosis 
or  Tnorhus  cceruleus,  and  may  be  remedied  by  keeping  the 
child    a  its  right  side  for  a  few  days. 

There  is  also  a  peculiarity  in  the  circulation  of  the  blood 
in  connection  with  the  Malpighian  bodies  of  the  kidney, 
closely  resembling  the  portal  circulation,  for  which  see 
structure  of  the  kidney. 


3 
H 

■A 


230 


RESPIRATION. 


CHAPTER  IX. 


c 

1. 
I* 

•I 


«R 


nnr  . 

»«!■  : 


R15SPIRATI0N. 

As  the  blood  circulates  thiough  the  different  parts  of  the 
body,  it  is  deprived  of  a  certain  amount  of  its  nutriti  ele- 
ments and  oxygen,  and  becomes  loaded  with  impurities, 
resulting  from  the  wear  and  tear  of  the  tissues  ;  hence  it 
becomes  necessar^^  not  only  that  fresh  supplies  of  nutriment 
and  oxygen  should  be  continually  added  to  the  blood,  but 
also  that  provision  should  be  made  for  the  removal  of  the 
impurities.  One  of  the  most  important  and  abundant  of 
the  impurities  is  carbonic  acid,  the  removal  of  which,  and 
the  introduction  of  fresh  quantities  of  oxygen,  constitute 
the  chief  purpose  of  respiration. 

THE  LUNGS. 

The  organs  of  respiration  are  the  lungs.  They  are  two 
in  number,  situated  one  in  each  of  the  lateral  cavities  of  the 
chest,  separated  from  each  other  by  the  mediastinal  space. 
They  are  provided  with  a  single  air  tube,  the  trachea,  which 
is  divided  into  two  branches,  the  right  and  left  bronchus, 
one  for  each  lung.  Each  bronchus,  on  entering  the  hilum 
of  the  lung,  divides  and  sub-divides  dichotomously  through- 
out the  entire  organ  until  the  branches  terminate  in  the 
lobular  bronchial  tubes.  Each  lung  is  surrounded  by  a 
serous  membrane — the  pleura.  That  portion  which  covers 
the  lung  is  called  the  visceral  layer,  and  is  connected  to  the 
lung  tissue  by  the  sub-serous  areolar  tissue  ;  it  is  then 
reflected  around  the  inner  surface  of  the  chest  forming  the 
parietal  layer.  These  two  layers  are  smooth,  moist  and 
covered  with  epithelium  ;  they  are  everywhere  in  contact, 


THE  LUNGS. 


231 


and  glide  readily  upon  each  other.  It  is  only  when  filled 
with  air  or  iluid  that  there  may  be  said  to  be  a  cavity 
between  thera. 

The  respiratory  apparatus  consists  essentially  of  a  thin, 
moist  membrane,  with  blood-vessels  on  one  side,  and 
air  or  aerating  fluid  on  the  other,  through  which  osmosis 
takes  place.  The  lungs  of  the  newt  consist  of  cylindrical 
sacs  running  the  entire  length  of  the  body,  into  which  the 
air  is  forced  by  a  sort  of  swallowing  movement,  and  is  after- 
wards regurgitated  to  make  room  for  a  fresh  supply.  In 
the  frog  nnd  turtle,  the  cavity  is  dividiid  into  smaller  com- 
partments by  thin  septa,  all  of  which  communicate  with 
the  central  cavity.  The  same  principle  or  plan  of  construc- 
tion obtains  in  the  higher  animals,  the  walls  of  the  cavity 
being  folded  and  refolded  in  order  to  increase  the  extent  of 
aerating  surface.  In  fishes  and  most  aquatic  animals  the 
respiratory  organs  are  in  the  form  of  gilh  or  branchice, 
which  are  foldings  of  mucous  membrane,  containing 
blood-vessels.  These  are  moved  by  muscles  so  as  to  bring 
them  into  contact  with  fresh  portions  of  water,  for  the  pur- 
pose of  aeration.  In  certain  of  the  lower  order  of  animals 
unprovided  with  Inng  cavities,  and  in  the  vegetable  king- 
dom, tracheal  openings,  or  stomata,  exist  for  the  interchange 
of  gases. 

Minute  Structure. — Each  lung  is  divided  into  lobes, 
three  for  the  right  and  two  for  the  left,  and  each  lobe  is  sub- 
divided into  lobules,  which  are  held  together  by  areolar  tis- 
sue. They  vary  in  size  form  yhf  to  ^V  of  an  inch  (2  to  .8  mm) 
in  diameter.  They  also  vary  in  shape  ;  those  on  the  surface 
are  large,  of  a  pyramidal  form,  with  their  bases  turned  towards 
the  surface ;  those  in  the  interior  are  smaller,  and  of  various 
forms.  Each  lobule  is  a  miniature  representation  of  the 
whole  organ  of  which  it  forms  a  part,  being  composed  of 
the  terminal  divisions  of  one  of  the  smaller  bronchial 
tubes  and  corresponding  air  cells,  blood  vessels,  nerves 
and    lymphatics,    all    held    together    by     areolar    tissue. 


'4 

I 

It 

) 

i 

I 

1 


232 


RESPIRATION. 


11 


c 

MM 

c 
I. 


MM 


'Hi 


Each  lobular  bronchial  tube,  on  entering  the  substance  of 
the  lobule,  divides  into  from  four  to  nine  branches  according 
to  the  size  of  the  lobule,  diminishing  in  size  until  they 
Fig.  77.  reach   a   diameter   of  -^  to  ^\^  of  an 

inch,  (.5  to  .2  mm).  They  are  then  con- 
tinued onwards,  their  sides  and  extremi- 
ties being  closely  covered  by  numer- 
ous saccular  dilatations — the  air  cells 
— in  consequence  of  which  the  tubes  lose 
their  identity,  as  cylindrical  tubes, 
and  present  the  character  of  irreg- 
ular canals  or  passages — the  so-called 
Lobule  of  the  human    intercellular  passages  (Fig,  77). 

lunsr ;  a,  bronchial  tube  rn,  .  ,,  n        i         i 

with  its  divisions ;  b,  in-         i  hc    air    ceils    are    smail    alveolar 

tercellular  passagfes;  c,  air  i  •    i  t  .  « 

cells.  recesses,  which  vary  from  yV  ^  ^iir  of 

an  inch,  (.3  to  .V^  mm)  in  diameter,  and  are  separated 
from  each  other  by  thin  septa.  They  communicate 
with    the     termin-  rig.  78 

al  bronchial  tubes 
which  thej'^  surround 
by  large  circular 
openings;  but  do  not 
communicate  with 
each  other  except 
through  the  tubes. 
In  these  small  bron- 
chial tubes  and  air 
cells,  the  cartilagin- 
ous and  muscular 
tissues  are  absent, 
and  the  mucous 
membrane  is  lined 
by  squamous  epith- 
elium, while  the 
trachea  and  bron- 
chi   are     lined    by 


Air  cells  of  lungs,  x  350 ;  a,  epithelium  ;  b,  fibres  of 
elastic  tissue  ;  c,  delicate  lining  membrane  of  air  cells, 
with  elastic  fibres  attached  t    it. — {KvUiker.) 


VESSELS  AND  NERVES. 


233 


columnar  ciliated  epithelium,  among  which  are  to  be  seen 
some   cup  or  goblet  cells  (p.  99). 

Vessels  and  Nerves. — The  pulmonary  artery  con- 
veys the  venous  blood  to  the  lungs  for  aeration.  It 
divides  into  branches  .which  accompany  the  bronchial 
tubes,  and  terminates  in  a  dense  capillary  plexus 
beneath  the  mucous  membrane  of  the  terminal  bron- 
chial tubes  and  air  cells.  Some  of  the  capillaries 
also  pass  into  the  septa,  between  the  air  cells  so  that 
both  sides  are  at  once  exposed  to  the  air.  The  blood,  puri- 
fied during  its  patisage  through  the  capillaries,  is  returned 
by  the  pulmonary  veins  to  the  left  auricle  of  the  heart.  The 
bronchial  arteries  supply  blood  for  the  nutrition  of  the 
lung.  They  arise  from  the  thoracic  aorta,  and  divide  into 
several  branches,  some  of  which  accompany  the  bronchial 
tubes  to  which  they  are  distributed,  and  terminate  in  the 
deep  bronchial  veins ;  others  are  distributed  to  the  areolar 
tissue,  and  terminate  partly  in  the  superficial,  and  partly  in 
the  deep  bronchial  veins  ;  whilst  a  few  ramify  upon  the  walls 
of  the  terminal  bronchial  tubes  and  air  cells,  and  terminate 
in  the  pulmonary  veins,  the  blood  having  been  purified  in 
its  passage  through  the  capillaries.  The  bronchial  veins, 
superficial  and  deep,  unite  at  the  root  of  the  lung,  and  empty 
on  the  right  side  into  the  vena  azygos  major,  and  on  the 
left  into  the  superior  intercostal.  The  lungs  are  also  abun- 
dantly supplied  with  lymphatics.  They  commence  in  irreg- 
ular spaces  or  lacunas  in  the  walls  of  the  air  cells,  or  bronchi, 
and  in  the  lymph  spaces  of  the  pleura  pulmonalis. 

Nerves. — The  lungs  are  supplied  by  the  anterior  and 
posterior  pulmonary  plexuses  of  nerves  formed  chiefly 
by  branches  from  the  pneumogastric  and  sympathetic 
nerves. 

MECHANISM   OF   RESPIRATION. 

The  movements  by  which  fresh  air  is  taken  into  the 
lungs,  and  by  which  it  is  again  expelled,  are  those  of 
inspiration  and  expiration.    This  is  called  the  mechanical 


•3 
■ft 


234 


RESPIRATION. 


C 

c. 

IL 

I- 

»i 

WV 
•n 


r 

inr  !■ 


«•»  K 


act,  in  contradistinction  to  the  chemical  which  relates  to 
the  changes  which  take  place  between  the  blood  and  the 
atmospheric  air. 

Inspiration. — During  inspiration  the  chest  is  enlarged 
in  every  direction,  but  chiefly  in  the  vertical.  The  latter 
is  effected  principally^by  the  conti'action  of  the  diaphragm, 
and  its  consequent  descent  towards  the  abdomen.  The  in- 
crease in  the  lateral  and  antero-posterior  diameters  is  due  to 
the  elevation  of  the  ribs,  both  in  front  and  at  the  aides.  The 
ordinary  muscles  of  inspiration  are  the  diaphragm,  exter- 
nal intercostals  (and  the  internal  in  front),  levatores  cos- 
tarum,  serratus^magnus,  and  serratus  posticus  superior. 
But  in  extraordinary  or  forced  inspiration,  as  during  a  ]iar- 
oxysm  of  asthma,  etc.,  the  shoulders  are  fixed  by  the  patient 
seizing'some thing  firmly,  and  the  serratus  magnus,  pectoralis 
major  and  minor,  trapezius,  subclavian  and  scaleni  muscles 
are  called  into  action.  The  scaleni  muscles  fix  the  upper 
ribs,  from  which  the  external  intercostals  act,  as  from  a 
fixed  point,  and  elevate  the  lower  ribs,  by  which  the  cavity 
of  the  chest  is  enlarged  laterally  and  antero-posteriorly.  This 
action  is  also  promoted  by  the  action  of  the  other  muscles 
previously  mentioned. 

Expiration. — Expiration  succeeds  inspiration,  after  a 
brief  interval,  and  is  accomplished,  in  ordinary  respiration, 
by  the  elastic  recoil  of  the  lungs  and  walls  of  the  chest,  after 
they  have  been  dilated,  and  partly  by  muscular  action. 
The  ordinary  muscles  of  expiration  are  the  abdominal 
muscles,  internal  intercostals  except  in  front,  serratus  posti- 
cus inferior,  and  triangularis  sterni.  The  extraordinary 
are  the  quadratus  lumborum,  latissimus  dorsi,  sacrolumbalis, 
and  those  which  assist  in  fixing  the  spine  and  pelvis.  In  diffi- 
cult breathing,  almost  every  muscle  in  the  body  is  made  sub- 
servie  to  the  action  of  respiration.  The  duration  of  in- 
spiration is  generally  less  than  expiration,  although  in  some 
instances  they  are  nearly  or  quite  equal,  and  thero  is  a 
slight  i)a   ^e  between  the  end  of  expiration  and  the  com- 


FREQUENCY  OF  RESPIRATION. 


285 


menceraent  of  the  next  inspiration,  and  also  between  the 
acts.  The  succession  of  these  acts  constitutes  the  respira- 
tory rhythm.  During  inspiration  and  expiration  a  sound  is 
heard  when  the  ear  is  applied  to  the  chest,  called  the  respir- 
atory  murmur.  It  is  longer  (|)  and  more  distinct  in  inspir- 
ation, and  is  best  heard  in  children,  hence  the  terra  puerile 
respiration.  The  rima  glottidis  is  also  opened  at  each 
inspiration  by  the  action  of  small  muscles,  and  is  closed  some- 
what at  each  expiration  by  the  elastic  recoil  of  the  parts. 
The  force  of  expiration  exceeds  that  of  inspiration  by  one- 
third. 

Frequency  of  Respiration  and  Ratio  to  the  Pulse. 
— The  number  of  respirations  in  a  healthy  adult  vary  from 
sixteen  to  twenty  in  a  minute.  The  proportion  of  respira- 
tory movements  to  the  pulsations  of  the  heart  is  about  one 
to  four,  and  when  this  proportion  is  departed  from  there 
is  reason  to  suspect  some  obstruction  to  the  aeration  of 
tlie  blood,  or  some  derangement  of  the  nervous  system. 
Any  great  disproportion  between  the  number  of  respirations, 
and  the  number  of  pulsations  or  the  amount  of  blood 
sent  to  the  lungs  to  be  aerated,  is  attended  with  dyspnoea. 
When  the  action  of  respiration  is  chiefly  confined  to  the 
diaphragm  and  abdominal  muscles,  as  in  pleurisy,  etc.,  the 
breathing  is  said  to  be  abdominal ;  but  when  chiefly  con- 
fined to  the  muscles  of  the  thorax,  as  in  peritonitis,  etc.,  it 
is  said  to  be  costal  or  thoracic. 

Quantity  of  Air  Respired. — The  quantity  of  air 
taken  in  at  each  inspiration  varies  from  twenty  to  thirty 
cubic  inches ;  this  is  called  breathing  or  tidal  air.  The 
quantity  which  an  adult  of  average  size  (five  feet  eight 
inches),  can  inhale  in  a  forced  inspiration  is  about  230 
cubic  inches  the  excess  being  called  complem£ntal  air. 
After  ordinary  expiration,  such  as  that  which  expels  the 
breathing  or  tidal  air,  a  certain  quantity  remains  in  the 
lungs,  which  may  be  expelled  by  a  forcible  expiration  ;  this 
is  called  reserve  or  supplemental  air.  A  quantity  still  re- 
13 


£88 


RESPIRATION. 


Fig.  79. 


c 
c 

I. 


IHf 


mains,  which  cannot  be  forced  out ;  this  is  called  residual 
air. 

The  respiratory  capacity  of  the 
chest  is  called  the  vital  capacity,  and 
it  varies  according  to  stature,  weight, 
and  age.  The  vital  capacity  of  an 
adult,  five  feet  eight  inches  in  height, 
is  about  230  cubic  inches  ;  and  for 
every  inch  in  height  above  this  stand- 
ard, the  capacity  is  increased  about 
eight  cubic  inches.  The  influence  of 
weight  is  not  so  marked  as  that  of 
height ;  but  it  tends  to  diminish  the 
respiratory  power,  when  beyond  a  cer- 
tain limit.  The  vital  capacity  in- 
creases from  fifteen  to  thirty -five  years 
of  age,  and  from  thirty-five  to  sixty- 
five  it  decreases  nearly  one  and  a  half 
cubic  inches  per  year. 

The  total  quantity  of  air  which 
passes  through  the  lungs  in  twenty- 
four  houi-s  varies  from  300  to  400 
cubic  feet,  depending  on  the  state  of 
the  health,  bodily  exertion,  etc.  If 
the  same  air  be  rebreathed  several 
times,  it  becomes  loaded  with  carbonic 
acid  and  animal  matter,  causing  head- 
ache, languor  and  depression,  and  if 
i  continued,  serious  results  will  follow 
Spirometer  for  measuring  sooncr  or  later.  Experience  has  shown 
!he'ir„g"'''°'*'"*'""'*"*°  that  the  minimum  quantity  of  air 
which  ought  to  be  allowed  for  each  person  confined  in 
prisons,  hospitals,  schools,  etc.,  is  about  1200  cubic  feet. 
Provision  should  also  be  made  for  a  constant  supply  of 
fresh  air,  and  the  removal  of  the  impure,  which  is  of  even 
greater  importance  than  the  mere  actual  cubic  space.     The 


n. 


I  NFL  UENCE  OB  NER  VES  IN  R  ESP  IRA  TION.      237* 


ventilation  should  be  such  as  will  supply,  at  least  from  1200 
to  1500  cubic  feet  of  fresh  air  for  each  person  per  hour. 

Influence  of  the  Nerves  in  Respiration. — The^ 
movements  of  respiration  are  presided  over  by  the  medulla 
oblongata,  into  which  may  be  traced  the  principal  excitor 
nerves,  and  from  which  proceed  the  principal  motor  nerves. 
The  chief  excitor  of  the  movements  of  respiration  is  the 
pneumogastric  nerve.  When  this  is  divided  on  both  sides 
in  the  dog,  the  number  of  respirations  are  diminished  about 
one-half,  and  irritation  of  its  trunk  is  followed  by  an  act  of 
inspiration.  The  respiratory  movements  are  caused  by  tlio 
presence  of  blood,  loaded  with  carbonic  acid,  in  the  capil- 
laries of  the  lungs,  which  makes  an  impression  on  the- 
periphery  of  the  pneumogastric  nerve.  The  other  excitors 
are  the  nerves  distributed  to  the  general  surface  of  the 
body;  but  especially  to  the  face.  A  current  of  cold  air,  or 
cold  water  dashed  on  the  face,  is  sufficient  to  cause  a  deep 
inspiration ;  and  a  similar  impression  on  the  chest  or  body, 
or  a  slap  on  the  buttocks,  will  excite  inspiratory  movements 
when  they  would  not  otherwise  commence,  as  in  the  new- 
born infant,  or  in  asphyxia.  The  first  plunge  into  water, 
as  in  swimming,  is  usually  accompanied  by  a  deep  inspira- 
tion. It  is  quite  probable  also,  that  the  sympathetic  nerves, 
which  receive  filaments  from  the  spinal  nerves  and  com- 
municate with  the  pneumogastric,  may  be  excitors  of  this 
function.  Tl  e  motor  nerves  concerned  in  the  function  of 
respiration  are  the  phrenic,  intercostals,  facial  and  spinal 
accessory.  The  motor  power  of  the  respiratory  nerves  is^ 
exerv'jised,  however,  not  only  in  the  muscles  of  respiration, 
but  also  on  those  which  guard  the  entrance  to  the  wind- 
pipe. Division  or  injury  of  the  medulla  oblongata  is 
followed  by  sudden  death  from  arrest  of  respiration- 
After  division  or  injury  of  the  spinal  cord  in  the  lower 
part  of  the  cervical  region,  inspiration  is  performed  by  the 
diaphragm  only,  and  when  injured  above  the  origin  of  the 
phrenic  nerve,  death  occurs  instantly,  because  of  the  inter- 


238 


RESPIRATION. 


c 
c 

c 
I. 
I* 

■t 

I. 

I 

m 


luption  to  all  commuiiicatiou  between  the  medulla 
oblongata  and  the  diapliragrn. 

The  respiratory  njovemcntH,  thougli  j)artly  voluntary,  arc 
in  ordinary  respiration  essontialiy  independent  of  tlio  will, 
I'or  example,  during  sleep,  coma  or  aniBstbesia,  the  respira- 
tory function  is  carried  on,  although  the  person  is  entirely 
unconscious  of  the  movements.  At  the  same  time,  it  is 
necessary  that  the  respiratory  actions  should  bo  ])artly 
under  the  direction  of  the  will,  since  they  are  subservient 
to  the  production  of  those  sounds  by  which  individuals 
communicate  their  ideas  to  each  other,  as  in  speaking 
singing,  etc. 

Modifications  of  the  Rksimratory  Movements. — 
These  are  coughing,  sneezing,  sighing,  yawning,  langhing, 
crying,  sobbing  and  hiccup.  Coughing  is  caused  by  any 
source  of  irritation  in  the  throat,  larynx,  trachea  or 
bronchial  tubes.  This  act  consists,  first,  in  a  full  inspiration, 
the  glottis  is  then  closed  and  a  violent  expiration  takes 
jdace,  by  which  a  sudden  blast  of  air  is  forced  up  the  air 
passages  by  the  diaphragm  and  abdominal  muscles,  forcing 
open  the  glottis  and  carrying  before  it  any  substance  that 
may  bo  present.  In  the  act  of  coughing,  the  abdominal 
nniscles  act  as  forcibly  on  the  abdominal  viscera  as  on  the 
lungs,  and  tend  to  the  expulsion  of  their  contents,  but  the 
voluntary  contraction  of  the  sphincters  prevents  any  escape 
at  the  openings.  The  difference  between  coughing  and 
sneezing  is,  that  in  the  latter  the  blast  of  air  is  directed 
more  or  less  completely  through  the  nose,  in  order  to  remove 
any  irritating  substance  there.  Sighing  is  simply  a  deep 
inspir  "  in  which  a  larger  quantity  of  air  than  usual  is 
nip'  .iter  the  lungs.    FawmT?^/ is  a  still  deeper inspira- 

.ud  is  accompanied  by   opening  the   mouth  widely, 

.  contraction  of  the  muscles  about  the  jaws.  In  laugh- 
ing, the  muscles  of  expiration  are  in  convulsive  movement, 
and  send  out  the  air  from  the  lungs  in  a  series  of  jerks,  the 
glottis  being  open.     Crying  is   very   nearly  the  same  as 


CHANGES  IN  THE  RESPIRED  AIR. 


289 


laughing,  altliough  occasioned  by  a  different  emotion. 
When  the  emotions  are  mixed,  an  expression  is  produced 
"  between  a  cry  and  a  laugh."  Sobbing  is  caused  by  a 
series  of  sliort  convulsive  contractions  of  the  diaphragm, 
the  glottis  being  closed.  Hiccup  is  caused  by  a  sudden 
convulsive  contraction  of  the  diaphragm,  the  glottis  sud- 
denly closing  in  the  midst  of  it;  the  sound  is  j)roduced  by 
the  impulse  of  the  column  of  air  against   the  glottis. 

In  speaking  and  singing,  the  vocal  chords  are  made  to 
vibrate  as  the  air  passes  over  them,  and  produce  sounds 
which  are  mouldei  into  words  or  notes  by  the  tongue, 
teeth,  lips,  etc. 

Chanoes  in  the  Respired  Air. — The  air  consists  of  a 
mixture  of  20.81  parts  oxygen  to  79.19  of  nitrogen,  in  100 
I)arts  by  volume,  carbonic  acid  from  .03  to  .00  parts  in  a 
thousand,  a  variable  amount  of  aqueous  vapour,  and  a 
trace  of  ammonia.  The  changes  ])roduced  on  the  atmos- 
pheric air  by  respiration  are — 1st,  an  increase  in  the  tem- 
perature equal  to  that  of  the  blood  ;  2nd,  an  increase  in 
the  quantity  of  carbonic  acid  and  aqueous  va])our ;  3rd,  a 
diminution  in  the  quantity  of  oxygen.  The  nitrogen 
remains  nearly  the  same,  and  a  small  quantity  of  organic 
matter  is  eliminated  by  the  lungs.  The  air  is  heated  by 
contact  with  the  interior  of  the  lungs  to  a  temperature  of 
about  98°  F. 

Exhalation  of  Carbonic  Acid  and  Water. — The 
presence  of  an  increased  amount  of  carbonic  acid  in  expired 
air,  may  be  demonstrated  by  breathing  through  lime  water, 
which  becomes  milky  by  the  formation  of  insoluble  calcium 
carbonate.  It  has  been  ascertained  that  there  are  about 
4.35  parts  of  carbonic  acid  in  100  parts  expired  air,  and 
subtracting  the  quantity  in  the  air  when  inspired,  leaves 
about  4.30  parts  per  cent,  by  volume,  which  is  eliminated 
from  the  lungs  at  each  ordinary  expiration.  This  would 
amount  to  about  sixteen  cubic  feet  per  day  of  carbonic 
acid,  or  nearly  eight  ounces  of  carbon.     The  elimination  of 


i 

1 

it 

♦ 

If 

i 


c 
c 

I' 
m 

IIM 

I.' 


inr  , 

Bnr  , 

m. . 


240 


RESPIRATION, 


•carbonic  acid  may  be  modified  by  a  number  of  circum- 
stances. 

Digestion  has  been  observed  to  be  attended  with  an 
increased  exhalation  of  carbonic  acid,  inost  distinct  about 
an  hour  after  eating ;  while  fasting,  on  the  other  hand, 
diminishes  it.  Alcohol,  etJier  and  chloroform  introduced 
into  the  system,  are  followed  by  a  diminution  in  the  quan- 
tity of  carbonic  acid  exhaled.  Exercise  increases  the  exha- 
lation of  carbonic  acid  to  about  one-third  more  than  it  is 
during  rest.  During  sleep,  on  the  other  hand,  it  is  dimin- 
ished, owing  to  the  quietness  of  the  breathing ;  but  directl}' 
after  'vaking,  the  amount  is  increased.  Age  and  sex 
influence  the  quantity  of  carbonic  acid  exhaled  ;  in  males 
it  ii.^.eases  from  eight  to  thirty  years  of  age,  remains 
stationary  from  thirty  to  forty,  and  then  diminishes  to 
extreme  age.  In  females,  the  quantity  exhaled  is  always 
less  than  in  males  of  the  same  age;  it  is  increased. from  the 
•eighth  year  to  the  age  of  puberty,  and  remains  stationary 
as  long  as  they  continue  to  menstruate,  but  when  men- 
struation ceases,  from  whatever  cause,  the  exhalation  of 
carbonic  acid  again  augments,  after  which  it  diminishes  to 
extreme  a je.  The  temperature  of  the  external  air  has  an 
important  influence  on  the  exhalation  of  carbonic  acid. 
Observations  made  at  various  temperatures  between  38° 
and  75°  F.  show  that  between  these  points  every  rise  equal 
to  10°  F.  causes  a  diminution  of  about  two  cubic  inches  in 
the  quantity  of  this  gas  exhaled  per  minute.  Cold,  on  the 
other  hand,  within  certain  limits,  increases  it.  Moisture  of 
the  air  also  favors  the  elimination  of  carbonic  acid  very 
materially.  The  respiratory  movements  influence  the  exha- 
lation of  this  gas.  When  the  respirations  are  increased  in 
frequency,  more  carbonic  acid  is  exhaled,  although  the  per- 
centage in  proportion  to  the  amount  breathed  is  less.  If 
the  air  have  been  previously  breathed,  the  quantity  of  car- 
bonic acid  exhaled  is  very  much  diminished.  It  should  also 
be   borne  in  mind,  that  the  continued  respiration  of  an 


AMOUNT  OF  OXYGEN  INHALED. 


241 


atmosphere  charged  with  the  exhalations  from  the  lungs 
and  skin,  is  a  most  potent  predisposing  cause  of  disease, 
especially  of  the  zymotic  class. 

Tlie  presence  of  an  increased  amount  of  aqueouLS  va'pour 
in  expired  air,  may  be  shown  by  breathing  upon  a  looking- 
glass,  or  polished  metallic  surface.  The  amount  of  aqueous 
vapour  exhaled  from  the  lungs  in  twenty-four  hours  may 
be  estimated,  in  temperate  climates,  at  from  ten  to  twenty 
ounces.  A  certain  amount  of  carbonic  acid  and  water  is 
also  eliminated  by  the  integument.  ATYimonia  is  an 
accidental  constituent  of  expired  air.  The  amount  of 
organic  matter  given  off  from  the  lungs  in  twenty-four 
hours,  is  about  three  grains. 

Amount  of  Oxygen  Inhaled. — There  is  always  less 
oxygen  in  expired  air,  than  in  the  same  quantity  of  air 
before  respiration.  Some  of  the  oxygen  unites  with  the 
carbon  in  the  lungs  to  form  carbonic  acid ;  some  is  used  in 
the  chemico-vital  changes  which  take  place  in  the  blood 
and  tissues,  and  some  is  also  used  in  oxidizing  other  sub- 
stances besides  the  carbon,  as  for  example,  sulphur  and 
phosphorus,  which  are  eliminated  in  the  urine  in  the  form 
of  sulphuric  and  phosphoric  acid.  Its  absorption  depends 
on  the  strong  chemical  affinity  of  hemoglobine  for  it.  The 
quantity  of  oxygen  absorbed  is  about  542  grains  per  hour, 
but  it  varies  in  different  persons,  and  in  the  same  person  at 
different  times.  It  is  increased  by  food,  especially  of  the 
farinaceous  kind,  and  is  diminished  during  fasting.  The 
interchange  of  gases  in  the  lungs  does  not  accord  with  the 
law  of  "  diffusion  of  gases,"  otherwise  the  proportion 
between  the  oxygen  consumed  and  the  carbonic  acid 
exhaled  should  never  vary.  Besides,  the  law  requires  that 
both  gases  should  be  free,  and  under  equal  pressure ;  while, 
in  reality,  the  gas  in  the  blood  is  dissolved,  under  pres- 
sure, and  is  also  separated  by  a  membrane  from  that  into 
which  it  is  to  be  diffused. 


•I 


242 


RESPIRATION. 


C 

c 

IE 
1. 
I- 

mv 
I. 


tta 


The  nitrogen  of  the  atmosphere  serves  only  to  dilute  the 
oxygen,  and  moderate  its  action  in  the  system.  Under 
ordinary  circumstances  there  is  very  little  difference  between 
the  quantity  of  nitrogen  inspired  and  exhaled.  The  absorp- 
tion of  nitrogen  is  increased  by  fasting;  while,  under 
opposite  circumstances,  it  is  diminished.  There  is  also  a 
small  quantity  of  nitrogen  given  off  in  the  form  of 
ammonia. 

Changes  in  the  Blood  in  Respiration. — 1st,  its  color 
is  changed  ;  2nd,  it  absorbs  oxygen  ;  3rd,  it  exhales  carbonic 
acid  and  aqueous  vapour,  small  traces  of  ammonia  and 
animal  matter  ;  -ith,  it  contains  more  fibrin,  and  the  temper- 
ature is  increased  from  1°  to  2°  F.  The  most  obvious  change 
is  tliat  of  color,  the  darls  venous  blood  being  exchanged 
for  the  bright  scarlet  of  arterial  blood.  The  causes  of  this 
change  have  been  already  discussed  in  the  chapter  on 
blood.  It  is  chiefly  due  to  the  absorption  of  oxygen,  which 
is  taken  up  principally  by  the  hemoglobine  of  the  corpus- 
cles and  partly  by  the  plasma,  and  carried  to  the  tissues ; 
and  to  the  exlmlation  of  carbonic  acid  which  exists  in  the 
blood.  Tlie  coipuscles  also  assume  a  I ''concave  shai)e, 
which  reflects  the  light  in  such  a  way  as  to  modify  the 
color.  Both  oxygen  and  carbonic  acid  exist  in  the  corpus- 
cles and  plasma  of  the  Ijlood,  partly  in  a  state  of  solution, 
and  partly  in  a  state  of  chemical  combination  ;  but  the 
corpuscles  are  the  chief  agents  concerned  in  the  absorption 
of  the  gases. 

The  exhalation  of  carbonic  acid  is  favored  by  the  moist 
condition  of  the  membranes  of  the  lung,  which  liquefies  the 
gas.  This  fact  may  be  demonstrated  by  filling  a  bladder 
■with  carbonic  acid,  and  then  placing  it  in  water ;  it  will 
soon  be  found  to  collapse  and  become  completely  emptied. 
Caibonic  acid  is  being  constantly  generated  in  the  blood, 
and  is  removed  by  exhalation  from  the  lungs,  as  fast  as  it 
is  produced;  but  if  respiration  is  obstructed  or  seriously 
impeded,  it  accumulates  in  the  blood,  and  may  cause  death 


EFFECTS  OF  ARREST  OF  RESPIRA  TION.       243 

by  its  poisonous  effects  on  the  nervous  system.  Carbonic 
acid  is  formed  in  three  different  ways  in  the  system :  1st, 
in  the  blood,  by  the  action  of  oxygen  on  certain  elements 
introduced  in  th'3  food,  as  glucose  and  fats,  giving  rise  to  a 
certain  amount  of  animal  heat;  2nd,  in  the  capillaries,  by 
the  union  of  oxygen  with  the  carbon  produced  by  the  dis- 
integration of  the  tissues ;  3rd,  in  the  lungs,  by  the  decom- 
position of  the  alkaline  carbonates. 

Effects  of  the  Arrest  of  Respiration. — When  res- 
|)iration  is  interfered  with  by  any  obstruction,  or  from 
whatever  cause,  the  circulation  of  blood  through  the  lungs 
is  retarded,  and  at  length  arrested.  This  prevents  tl  ) 
exit  of  blood  from  the  right  ventricle,  and  is  followed  by 
venous  congestion  of  the  nervous  centres,  and  all  the  other 
parts  of  the  body.  Besides,  only  a  very  small  quantity  of 
blood  finds  its  way  into  the  left  side  of  the  heart,  and  this 
is  venous  also.  Hence,  in  death  from  asphyxia,  the  left 
side  of  the  heart  is  nearly  empty,  while  the  lungs,  right 
side  of  the  heart  and  veins,  are  gorged  with  venous  blood. 
The  cause  of  the  retention  of  blood  in  the  lungs  is  due  to 
the  non-elimination  of  the  caibonic  acid  ;  for  blood  loaded 
with  this  gas  does  not  pass  freely  through  the  capillaries. 
The  fatal  result  is  due,  to  some  extent,  to  the  weakened 
action  of  the  right  side  of  the  heart,  in  consequence  of  its 
over-distension ;  and  also  to  the  venous  congestion  in  the 
medulla  oblongata  and  nervous  centres.  The  time  which 
is  necessary  for  life  to  be  destroyed  by  asphyxia  varies 
from  one  and  one-half,  to  four  minutes.  In  new-born  and 
young  animals,  longer  time  is  required  than  in  older  ones, 
because  in  the  formet  the  respiratory  changes  in  the  tissues 
are  much  less  active.  Animals  will  recover  after  simple 
deprivation  of  air  for  four  minutes,  but  submersion  in  water 
for  \\  minutes  destroys  life  completely.  This  is  owing,  in 
all  probability,  to  the  filling  of  the  lungs  with  water.  In 
drowning,  very  few  persons  recover  who  have  been  sub- 
merged more  than  three  or  four  minutes.     Cases  have  been 


■I 


2H 


RESPIRATION, 


rc^cordod  in  which  recovery  took  place  after  the  lapse  of 
from  fifteen  minutes  to  half  an  hour;  but  in  these  instances 
it  is  probable  that  a  state  of  synco[)e  had  come  on  at  the 
moment  of  immersion. 


CHArTER  X. 


C 

c 

mm 

r 

I- 


r. 


ANIMAL   HEAT,   LIGHT,   AND   ELECTRICITY. 

Heat. — This  is  closely  connected  with  the  process  of 
respiration.  The  average  tem])erature  of  the  human  body 
varies  from  98°  to  100°  F.;  birds  from  100°  to  111°  F.; 
iishos  and  reptiles,  about  51°  F.  In  mammals  and  birds  the 
temperature  of  the  blood  and  internal  organs  is  always  very 
much  above  the  external  air,  and  they  are  therefore  called 
"  irartn-hlooded  animaW  In  fishes  and  rci)tilo8,  on  the 
other  hand,  the  temperature  of  their  bodies  (litters  but  little 
from  that  of  the  medium  which  they  iidiabit,  hence  they 
are  called  "  cold-hloodcd  animals."  In  both  classes,  how- 
over,  there  is  an  internal  source  of  heat,  but  it  is  more 
active  in  the  one  tlian  the  other.  Even  in  vegetables  a  cer- 
tain amount  of  heat-producing  jiovver  is  occasionally  mani- 
fest, as  for  example,  in  the  flowering  of  plants,  malting  of 
barley,  etc.  In  disease,  the  temperature  of  the  body  may 
deviate  somewhat  from  the  natural  standard,  as  e.g.,  in  scar- 
latina, typhoid  fever,  etc.,  it  rises  as  high  as  lOG"  or  lO?**  F. 
In  cholera,  on  the  other  hand,  it  often  falls  as  low  as  78°  or 
79"  F.  Continued  high  temperature  in  fever  usuall}'^  indi- 
cates a  fatal  issue.  The  highest  temperature  yet  observed 
was  reported  by  Dr.  Teale,  Eng.  in  a  case  of  spinal  injury, 
in  which  the  temperature  reached  122"  F.  The  patient 
recovered.     In  some  cases  of  yellow  fever,  a  remarkable  rise 


PRODUCTION  OF  ANIMAL  HEAT. 


245 


takes  place  very  soon  after  death,  in  one  iriHtanco  afl  liigh 
as  113°  F.,  fifteen  ininuteH  after  death.  The  temperature  of 
tlie  body  in  liealth,  is  ahout  1)"  F.  lower  during  sleep  than 
while  awake.  It  is  raised  by  exercise,  and  also  after  eating. 
The  temperature  of  the  now-born  child  is  1"  F.  higher  than 
in  the  adult. 

TnKoiiY  OF  THE  PRODUCTION  OF  Animal  Heat. — There 
have  been  many  theories  regarding  this  subject.  Lavoisier 
supposed  that  the  oxygen  taken  into  the  lungs  combined 
with  the  carbon  of  the  blood  and  formed  carbonic  acid 
which  was  at  once  eliminated,  the  f-ame  amount  of  heat 
being  produced  as  if  the  oxidation  of  a  "iimilar  quantity  of 
carbon  in  wood  or  coal  ha<l  taken  place,  and  that  the  heat 
thus  developed  radiated  to  the  different  ])arts  of  the  body. 
This  view  was,  however,  soon  ascertained  to  be  incorrect, 
inasmuch  as  the  heat  of  the  lungs  was  found  to  be  no  greater 
than  the  rest  of  the  body.  It  was  also  shown  that  the  car- 
bonic acid  is  formed  principally  in  the  blood  and  tissues, 
and  that  the  oxygen  is  taken  up  by  the  blood  corpuscles  and 
carried  away  in  the  general  circulation.  According  to  Lie- 
big,  the  heat  of  the  aninml  body  is  pro<lucod  by  the  oxida- 
tion or  combustion  of  certain  elements  of  the  food,  while 
circulating  in  the  blood,  as  sugar,  and  fats.  He 
therefore  divided  the  food  into  two  classes, — Jst,  The  plantic 
elements  of  nutrition,  which  are  used  in  the  building  up  of 
the  tissues,  as  albumen,  fibrin,  casein,  musculai*  tissue,  etc. 
2nd,  The  elements  of  resjnratlon,  as  starch,  sugar,  and  fats, 
which  are  chiefly  used  in  the  ])roduction  of  animal  heat, 
being  oxidized  in  the  ci  ulation,  and  eliminated  in  the  form 
of  carbonic  acid  and  water  by  the  lungs.  This  theory, 
filightly  modified,  is  the  one  which  i.s  most  generally 
received. 

The  ])roduction  of  animal  heat,  then,  is  a  phenomenon 
which  results  partly  from  the  oxidation,  or  combustion,  of 
certain  elements  of  the  food,  and  partly  from  the  chemico- 
vital  changes  which  take  place  in  the  blood,  and  the  difier- 


1 
(I 

I 


246 


HEAT,  LIGHT  AND  ELECTRICITY. 


c 

c 


I. 
I- 

■r 

«v 

MM 


Ik' 


ent  orgariH  of  tlio  body.  Every  chaiigo  in  tlio  condition  of 
tho  organic  constituents  of  the  body,  in  which  their  ele- 
ments enter  into  new  combinations  with  oxygen,  must  be  a 
source  of  the  devclopement  of  heat ;  and  the  amount  of 
oxygen  consumed  bears  a  certain  relation  to  tho  amount  of 
heat  produced,  the  same  amount  of  heat  being  produced, 
whether  the  union  be  raj)id  or  slow.  It  is  also  found  that 
the  (piantity  of  heat  generated  in  tho  body  is,  "  ccvterispar- 
ibi(s,"  in  direct  proportion  to  the  activity  of  the  respiratory 
process.  For  example,  in  birds,  whoso  function  of  respira- 
tion is  very  active,  the  animal  tcmj)crature  is  very  high 
(111°  F.),  while  in  mammals,  whose  respiration  is  less  active 
it  is  less  (98°  to  102«  F.)  In  tishos  and  reptiles,  both  the 
respiration  and  tho  animal  heat  are  much  lower  than  in 
either  of  tlie  preceding  (51"  F.).  Besides,  the  quantity  and 
cpiality  of  the  food  used  are  different  in  different  climates 
and  seasons,  for  example,  larger  (piantities  of  fats  and  oils 
are  used  in  the  food  in  cold  than  in  warm  climates,  in  order 
to  supply  nuiterial  for  the  maintenance  of  animal  heat. 
Even  in  temperate  climates,  more  fats  are  used  in  winter 
than  in  summer. 

Influence  of  the  Nervous  System  in  the  Produc- 
tion OF  Anijial  Heat. — It  has  been  observed  that  after 
the  division  of  the  nerves  of  a  limb  the  temperature  falls,and 
this  diminution  of  heat  is  still  more  decidedly  marked  in 
cases  of  }>aralysis  ;  e.g.,  the  hand  of  a  paralyzed  arm  was 
found  to  be  70"^  F.,  while  that  of  the  sound  side  had  n  tem- 
perature of  92*^  F.  Again,  when  death  is  caused  by  a  severe 
injury,  or  removal  of  the  nervous  centres,  or  in  poisoning  by 
woorara,  etc.,  the  temperature  of  the  body  rapidly  falls,  even 
though  artificial  respiration  be  kept  uj).  On  the  other 
hand,  severe  injuries  of  the  nervou?  system  are  sometimes 
followed  by  the  direct  opposite  eff'ect  This  is  supposed  to 
be  due  to  the  dilatation  of  the  arteries,  in  consequence  of 
which  the  blood  reaches  the  part  supplied  by  those  iterves 
in  larger  quantities;  the  nutrition  is  therefore  more  active. 


REGULA  TION  OF  THE  HE  A  T  OP  THE  BOD  V.      247 


Certain  emotions  of  the  mind  may  cause  a  momentary  in- 
crease of  temperature,  while  others  cause  a  diminution. 
These  circumstances,  however,  do  not  prove  that  heat  is 
produced  by  mere  nervous  action  independent  of  any  chem- 
ical change.  All  the  functions  of  the  organism,  as  nutrition, 
secretion,  excretion,  etc.,  are  under  the  influence  of  the 
nerves,  and  when  they  are  divided,  or  otherwise  injured,  or 
paralyzed,  chemico-vital  action  is  in  great  measure  sus- 
pended. 

Regulation  of  the  Temperature  of  the  Body.  — 
The  temperature  of  the  body  is  rendered  uniform  partly  by 
loss  of  heat  by  radiation,  and  conduction  ;  but  chiefly  by  the 
evaporation  which  is  continually  taking  place  on  its  sur- 
face and  to  a  small  extent  in  the  air  passages.  The  intro- 
duction of  food  and  drink  at  a  lower  temperature  than  the 
body,  and  the  removal  of  the  excreta,  also  abstract  a  small 
amount  of  heat.  Evaporation  of  the  perspiration  produces 
cold,  on  the  principle  that  "  when  a  fluid  passes  into  a  state 
of  vapour  heat  becomes  latent,"  and  hence  the  loss  of  heat 
will  depend  upon  the  amount  of  evaporation.  When  the 
atmosphere  contains  much  moisture  the  evaporation  is  partly 
suspended,  and  all  the  effects  of  excessive  heat  are  made 
more  apparent  than  in  a  dry  atmosphere,  in  which  a  greater 
amount  of  evaporation  takes  place,  and  consequently  a 
greater  amount  of  heat  is  removed  from  the  system.  Per- 
sons have  been  known  to  remain  for  several  minutes  in  a 
dry  atmosphere,  heated  to  250'^F,  without  injury,  the  evap- 
oration being  sufficient  to  keep  the  temperature  of  the  body 
within  certain  limits.  Such  a  degree  of  heat  in  a  moist 
atmosphere  would  be  certain  to  cause  serious  injury. 

In  fevers  and  inflammation,  the  skin  is  hotter  than  in 
health,  and  is  also  dry ;  this  is  owing  to  the  arrest  of  the 
natural  secretion  or  perspiration,  in  consequence  of  which 
there  is  little  or  no  evaporation  to  produce  cold.  In  such 
oases  great  benefit  will  be  derived  from  sponging  the  body 
frequently  with  cold  or  tepid  water. 


■ul 

n 

■it 

H 

if 

I 


248 


HEAT,  LIGHT  AND  ELECTRICITY. 


c 
c 

c 

I- 


LIGHT 

The  evolution  of  light  from  the  living  liuman  body,  is  a 
phenomenon  of  rare  occurronco.  Luminous  exhalations  have 
been  freijuontly  observed  in  burial  groundn,  and  a  luminous 
appearance  has  been  Homotimos  notituxl  in  newly  dissected 
subjects  in  the  dark.  This  is  due  to  the  development  of  [)ho.s- 
phoretted  hydrogen  during  decomposition  of  the  tissues.  A 
lun)inous  appoaiance  has  been  observed  in  old  sores  in  the 
living  subject,  which  wore  in  a  state  of  <lecomposition.  It 
is  also  said  that  an  evolution  of  light  has  Ixien  noticed,  in 
two  or  three  instances,  in  pati«;nts  in  the  last  stage  of 
phthisis.  The  light  in  these  cases,  was  observed  to  play 
around  the  face,  and,  in  all  probability  proceeded  from  the 
breath,  which  had  a  pecidiar  smell,  and  was  probably  charg- 
ed with  phosphoretted  hydrogen.  The  urine  also,  in  some 
instances,  has  a  luminous  appearance,  depending  upon  the 
presence  of  unoxidized  phosphorus  which  it  contains.  The 
breath  of  an  animal  may  be  rendered  distinctly  luminous  by 
injecting  phosphorus  dissolved  in  olive  oil,  in  the  proj)or- 
tion  of  two  grains  to  the  ounce,  into  the  veins. 


ELECTRICITY. 

This  is  generated  by  cheniical  union  or  decomjwsition, 
heat,  and  motion  or  friction.  There  are  no  two  parts  of  the 
body,  except  probably  those  of  oi)posite  sides,  whose  elec- 
trical condition  is  precisely  the  same.  This  depends  on  the 
difference  in  the  functional  activity  of  the  parts ;  e.g.,  the 
skin,  and  most  of  the  internal  membranes,  are  in  opposite 
electrical  states.  Electrical  car  rents  exist  in  muscles  and 
nerves ;  this  may  be  demonstrated  by  means  of  the  galvano' 
meter.  The  direction  of  the  current  is  constant  in  each 
muscle  ;  but  different  muscles  have  different  currents,  c.^.,  in 
the  gastrocnemius  of  the  frog,  the  direction  is  from  the  foot 
towards  the  body ;  while  in  the  sartorius  it  is  the  reverse. 
But,  taking  all  the  muscles  of  the  limb  together,  the  differ- 


ELECTRICITY. 


240 


ont  currents  are  ho  unevenly  balanced,  that  a  constant  cur- 
rent i8  establiohed  in  one  direction  of  the  limb,  and  this,  in 
the  frog,  is  from  the  foot  towards  the  body.  The  current  of 
a  man's  arm  is  from  the  shoulder  to  the  fingers. 

When  the  two  cut  ends  of  a  muscle  are  placed  against  the 
electrodes  of  a  galvanometer,  a  very  slight  deflection  of  the 
needle  is  observed,  and  tlio  same  is  the  case  with  two  points 
of  a  longitudinal  section  which  are  equally  distant  from  the 
middle  of  the  muscle.  But  the  most  i)Owerful  influence  on 
the  galvanometer  is  produced  when  to  th»  urface  of  a  muscle 
is  applied  one  of  the  electrodes,  and  the  cut  end  bnjught  in 
contact  with  the  other.  These  results  may  be  obtained  with 
small  portions  of  muscle,  even  with  a  single  fasciculus. 
Hence,  it  would  appear,  that  each  integral  particle  or  sar- 
cous  element  is  a  centre  of  electromotive  action,  and  con- 
tains within  it  positive  and  negative  elements,  the 
arrangement  of   which    represents   a   galvanic   pile   thus  . 


+ 


It  is  supposed  by  some,  that  the  light  spots  in  the  mus- 
cular fibrillsG  are  electro-positive,  and  the  dark  spots 
electro-negative.  It  has  also  been  observed,  that 
during  contraction  of  the  muscle  the  electric  current  is 
dimiiiifched.  This  may  be  exemplified  by  means  of  a 
connnon  battery.  It  will  be  observed  that  when  the  i)oles 
are  held  tightly  in  the  hands,  and  the  muscles  firmly  con- 
tracted, the  shock  is  not  so  readily  transmitted  as  when  they 
are  held  gently.  Since  electricity  is  transmitted  both  by 
the  muscles  and  nerves,  it  is  probable  that  contraction 
of  the  former  alters  slightly  the  relative  position  of  some  of 
the  i:)ositive  or  negative  elements,  and  in  this  way  the 
power  of  conducting  by  the  muscles  is,  to  a  certain  extent 
destroyed. 

There  is  also  an  electric  current  in  nerves,  similar  to  that- 
in  the  muscles.  When  a  small  piece  of  nerve,  recently  ob- 
tained from  the  living  body,  is  placed  so  that  its  surface  rests- 
on  one  of  the  electrodes,  and  its  cut  extremity  touches  the 
other,  a  considerable  deflection  of  the  needle  is  produced  in 


1 


Tit; 


250 


HEAT,  LIGHT  AND  ELECTRICITY. 


c 
c 

NM' 

I. 
I- 

m. 

MV 

wu 

f 

«^ 

Hte'i 

mr  ( 

»l5t  ' 

nu  1.. 


a  direction  which  indicates  that  tlie  current  is  from  the  in- 
terior to  the  exterior  of  the  nerve.  If  the  cut  ends  are 
applied  to  the  two  electrodes  respectively,  no  marked  effect 
is  observed.  The  most  powerful  effect  is  produced  by 
doubling  the  nerve  in  the  middle,  and  applying  both  ends 
to  one  electrode  and  the  loo])  to  the  other.  The  nervous 
current,  like  the  muscular,  is  due  to  tiie  electromotor  action 
of  the  molecules  of  the  nerve.  The  term  elecivotonus,  is  ap- 
j)lied  to  the  condition  of  the  nerve  which  exists  during  the 
time  of  electric  stimulation.  The  irritability  of  the  nerve  is 
increased  in  the  region  of  the  negative  pole  or  kathode,  and  is 
known  as  l:atdcctroionu8,yi\\\\ii,  it  is  diminished  in  the  region 
of  the  positive  pole  or  anode  and  is  known  as  the  condition 
of  aneledrotonus.  Electric  currents  are  conveyed  by  nerves 
as  well  in  one  direction  as  another.  The  body  would  become 
surcharged  with  electricit}''  were  it  not  that  the  equilibrium 
is  maintained  by  the  free  contact  which  is  continually  taking 
])lace  between  it  and  surrounding  bodies.  It  is  only  when 
the  body  is  insulated  that  it  becomes  apjmrent.  The  electri- 
city of  man  is  generally  positive;  of  woman,  more  frequently 
negative  ;  and  irritable  men,  of  sanguine  temperament,  have 
more  free  electricity  than  i)hlegmatic  persons.  In  sofne  per- 
sons a  crackling  noise  is  produced  when  articles  of  dress,  worn 
next  the  skin,  are  being  removed,  especially  in  dry  weather. 
A  case  of  a  lady  is  mentioned  in  the  American  Journr.l  of 
Medical  Sciences  (1838),  in  whom  the  generation  of  elec- 
tricity was  so  great,  that  whenever  she  was  insulated  by  a 
carpet,  or  any  other  feebly  conducting  medium,  sparks  pass- 
ed between  her  body  and  any  object  she  approached.  As  many 
as  four  sparks  per  minute  would  pass  from  er  finger  to  the 
brass  ball  of  the  stove,  at  the  distance  of  one  and  a  half 
inches.  This  phencmenon  was  accompanied  with  a  good 
deal  of  pain. 

In  some  persons,  a  sufficient  amount  of  electricity  may 
be  generated,  when  insulated  by  a  carpet,  to  enable  them 
to  ignite  a  recently  extinguished  gas  jet,  by  means  of  the 
isparks  which  pass  from  the  fingers. 


ELECTRICITY. 


2.U 


SoTie  animalH  pOvSsess  organs  in  which  electricity  may 
bo  generated  and  accumulated  in  large  quantities,  and  from 
which  it  may  be  discharged  at  will.  The  most  remarkable 
examples  are  to  be  found  in  certain  fishes,  the  best  known 
of  whicli  are  the  torpedo,  or  electric  ray,  and  the  gymnoius, 
or  electric  eel.  The  shock  of  the  gymnotus  is  sufficiently 
powerful  to  kill  small  animals;  that  of  the  torpedo  is  not 
severe,  but  sufficient  to  benumb  the  hand  that  touches  it. 

Sparks  of  electricity  may  be  produced  in  most  animals 
having  a  soft  fur,  by  rubbing  the  surface,  especially  in  hot 
weather.  This  may  be  easily  demonstrated  by  smoothing 
the  back  of  a  cat  with  the  hand,  in  a  darkened  room,  rub- 
bing the  horse  in  a  dark  stable,  or  by  scraping  sugar  in  the 
loaf  in  a  dark  pantry. 


•4 


5 

it 

1 


■H 


I 


252  SECRETING  GLANDS  AND  THEIR  SECRETIONS. 


CHAPTER  XI. 


SKCRETINU   GLANDS  AND   THEIR   SECRETIONS. 


c 
c 

i. 


THE   LIVER, 

This  is  the  largest  gland  in  the  body,  situated  in  the  right 
hypochondriac  region,  and  extending  across  the  epigastric 
into  the  lefthypochondrium.  It  measures  from  ten  to  twelve 
inches  from  side  to  side,  and  from  six  to  seven  from  before 
backwards,  and  weighs  about  three  to  four  pounds.  It  con- 
sists oi' jive  lobes,  which  are  mapped  out  on  its  under  suriace 
hy  Jive  fissures.  It  is  mainly  divided  into  two  lobes,  the  right 
and  left,  by  a  longitudinal  fissure,  the  anteriv)v  portion  of 
which  is  called  the  umbilical  fissure,  and  the  posterior 
part,  the  fissure  for  the  ductus  venosus.  The  right  lobe 
is  six  times  as  largo  as  the  left,  and  presents  on  its  under 
surface  the  lobus  quadrstus,  lobus  ca^idatus,and  lobusSpigelii 
separated  from  each  other  by  the  transverse  fissure,  the  fis- 
sure for  the  gal'-bladder  and  the  fissure  for  the  vena  cava. 
The  transverse  fissure  is  sometimes  called  the  hilum,  and  is 
situated,  as  in  the  lungs,  kidneys,  sj)leen,  etc.,  nearer  the 
posterior  than  the  anterior  border.  The  liver  is  intended 
mainly  for  the  secretion  of  bile,  and  is  also  supposed  to  ef- 
fect important  changes  in  certain  constituents  of  the  blood 
in  its  passage  through  the  gland. 

Minute  Structure. — The  liver  is  surrounded  by  a  re- 
flection of  the  peritoneum,which  constitutes  its  serous  cover- 
ing. This  is  attnehed  to  the  substance  of  the  gland,  except 
at  its  point  of  cttachment  to  the  diaphragm  and  in   the 


r^ 


THE  LIVER. 


263 


bottom  of  tlie  different  fissures,  by  fine  areolar  tissue.  The 
substance  of  the  liver  consists  of  lobules  held  together  by 
delicate  areolar  tissue,  the  ramifications  of  the  portal  vein, 
hepatic  artery  and  ducts,  hepatic  veins,  nerves  and  lymph- 
atics. 

The,  lohule.s  (acini)  are  small,  oval  or  roundish  bodies, 
about  the  size  of  a  millet  seed  measuring  from  Vn  tf>  ixs  '>f^ 
an  inch  (2.5  to  1.2  mm)  in  diameter.  They  surround  tho 
the      small      sublobular  fik.  so. 

branches  of  the  hejiatic 
vein,  to  which  each  is 
connected  at  its  base 
by  a  small  intralobular 
branch.  When  divided 
longitudinally,  they  pre- 
sent a  foliated  margin, 
and  on  a  transver.se  sec- 
tion, they  have  a  poly- 
ii'onal  outline.  When  one 
of  the  sublobular  hepatic 
vnns  is  laid  open,  the 
bases  of  the  lobules  may 
1)6  seen  through  the  thin 
walls  of  the  vein  on 
which  they  rest.  The 
base  of  each  lobule  i^re- 
sents  a  polj'^gonal  outline, 
in  the  centre  of  which 
may  be  seen  the  orifice  of  the  intralobular  vein.  This  gives 
them  the  appearance  of  a  layer  of  tesselated  or  pavement 
epithelium. 

Structure  of  the  Lobules. — Each  lobule  is  a  miniature 
representation  of  the  wliole  gland  of  which  it  forms  apart. 
It  consists  of  a  mass  of  cells,  a  plexus  of  biliary  ducts,  an 
intralobular  vein  (which  is  the  commencement  of  the  hepatic 
vein),  arteries,  nerves,  and  lymphatics. 


Longitudinal  section  of  a  portal  canal  contaln- 
'"tr.(P)  portal  vein  ;  (a)  hepatic  artery,  and  (d)  he- 
patic duct.  Lobules  are  to  be  seen  to  the  rijjht- 
and  left.aiid  also  shining  through  the  thin  wall  of 
the  vein;  in  the  centrs  of  each  lobule  is  seen  the 
intralobular  vein  ;  a,  a,  portion  of  the  '  Mial 
from  which  the  vein  has  been  removea  ;  b,  open- 
ings of  the  interlobular  veins. 


.4 

1 

.1 

> 

J 


254  SECRETING  GLANDS  AND  THEIR  SECRETIONS. 


c 
c 

MM 

I. 

^ 


I 

Cnr 

m-. : 
X.U 


The  hepatic  cells  form  the  chief  ma.ss  of  the  substance  of  a 
lobule  •  they  lie  in  the  interspaces  of  the  capillary  plexus,  so 
as  to  fonu  rows,  which  radiate  from  the  centre  to   the  cir- 

Fi>r.  81. 
h  B 


nopatio  loliuK'.  Ill  tlio  coiitrc  is  st'i'ii  tlio  intralobular  vein  ;  vp,  ttnuination  of  the  por- 
tal vein  around  tlio  lohulc,  from  which  a  cai)ilUiry  pluxus  proceeds  towards  the  centre  in 
the  lueshes  of  which  arc  seen  the  liopatic  cells  ;"  b,  b,  biliary  duuts,  arising  within  the 
lobule.    (Claude  llcrnard.) 

cumference  of    the  lobule  (Fig.  81).     They  are  generally 

spheroidal  in  sliape,  but   may   be   polygonal  from  mutual 

pressure,  and  vary  in   size,   from  ^j^^^  to  ^o^ory   of  an  inch 

Fijf.  82.  (25  fo  12.5  ijuum.)  in  diameter.     Each  cell 

contains  a  distinct  nucleus,  sometimes  two, 

and  in  the  interior  of  the  nucleus  a  highly- 

refiacting    nucleolus,  and    some  granular 

matter.    The  contents  of  the  cell  are  viscid, 

and  contain  yellow  particles   of  colouring 

Hepatic  tells.  (Frey.)    matter,  and  some  oil  globules. 

BiLiAuv  Ducts. — These  commence  within  the  lobule  by 
a  minute  plexus  of  ducts  (bile  capillaries),  with  which  the 
cells  are   in    immediate  contact.     The  ducts  then  form  a 


HEPATIC  VESSELS. 


255 


plexus  between  the  lobules  (interlobular),  and  the  inter- 
lobular benches  unite  into  vaginal  branches,  which  lie  in 
the  portal  canals.  These  branches  finally  join  to  form  two 
large  trunks,  which  leave  the  liver  at  the  transverse  fissure, 
and  uniting  form  the  hepatic  duct. 

Portal  Vein. — The  portal  vein,  on  entering  the  trans- 
verse fissure  of  the  liver,  divides  into  two  branches,  one  for 
each  lobe,  which  are  situated  in  the  portal  canals,  to- 
gether with  the  branches  of  the  hepatic  artery  and  duct, 
nerves  and  lymphatics.  These  vessels  are  surrounded  by 
areolar  tissue,  continued  inwards  from  the  transverse  fissure 
of  the  liver,  called  Glisson's  capsule.  The  portal  veins,  in 
their  course  in  those  canals,  give  off*  vaginal  branches,  which 
form  a  plexus.  From  this  plexus  and  from  the  portal  vein 
itself,  small  branches  are  given  oft',which  pass  between  the 
lobules  and  cover  their  external  surface,  called  interlobular  ; 
these  then  pierce  the  lobules,  and  form  a  capillary  i)lexus 
within    each,   from    which  arises  the  intralobular  vein. 

Hepatic  Artery. — This  takes  precisely  the  same  course 
as  the  portal  vein  and  hepatic  duct.  It  is  intended  chiefly 
for  the  nutrition  of  the  liver.  It  gives  off"  in  the  portal 
canals  the  va.ginal  branches,  which  supply  the  coats  of 
the  portal  vein  and  hepatic  ducts,  and  also  interlobu- 
lar branches,  which  pass  between  the  lobules ;  the  latter 
pierce  the  lobules,  and  terminate  in  the  radicles  of  the  intra- 
lobular vein.  They  are  supposed  by  some  to  terminate  in 
the  radicles  of  the  portal  vein,  but  this  is  improbable. 

Hepatic  Veins. — The  hepatic  veins  commence  in  the  in- 
terior of  the  lobules  in  the  intralobular  veins,  which  arise  in 
the  centre  of  the  lobules,  and  leave  them  at  their  bases  to 
join  the  sublobular  veins.  The  sublobular  veins  unite  to 
form  larger  branches,  and  these  join  again  to  form  the 
large  hepatic  veins,  which  terminate  in  the  inferior  vena 
cava. 

Fv>r  the  secretion  of  the  bile,  and  its  function,  see  chap- 
ter on  digestion. 


1 


256  SECRETING  GLANDS  AND  THEIR  SECRETIONS. 


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THE   KIDNEY   AND   ITS   SECRETION. 

The  kidneys  are  intended  for  the  secretion  of  urine.  They 
are  situated  in  the  back  part  of  the  abdotninal  cavity,  one 
in  each  lumbar  and  hypochondriac  region,  extending  from 
the  eleventh  rib  to  within  two  inches  of  the  crest  of  the 
ilium.  The  rijjht  is  somewhat  shorter  and  situated  a  little 
lower  than  the  left.  They  are  invested  by  a  thin,  smooth, 
fibrous  capsule,  which  is  very  easily  removed  from  the  sur- 
face of  the  gland,  and  weigh  from  four  to  six  ounces  each. 

Structure. — The  kidney  consists  of  two   different  sub- 
stances, an  external  or  cortical,  and  an  internal  or  medul- 
lary substance.      The  cortical  substance  forms  about  three- 
Fig.  83.  fourths  of  the  whole  gland,  is  reddish 
in  color,  soft,  granular,  and  friable  in 
texture,  and  presents  numerous   red- 
dish bodies  (the  Malpighian    bodies) 
in  every  part  of  it,  excepting  towards 
the  free  surface.     It  is   composed   of 
the  convoluted  tubuli  uriniferi,  blood 
vessels,  nerves   and  lymphatics,  held 
together  by  a  small  quantity  of  are- 
olar tissue.     The   cortical   substance 
is  from  ^  to  i^   an  inch   in  thickness 
opposite  the  base  of  each  pyramid,and 
is  called  the  cortical  arch.      It   also 
sends  numerous  prolongations  inward 
Srf^maVkThf  X-rco"  towards  the  sinus,  between  the  pyra- 

mids ;    these  are  called    the  cortical 
columns  or  columns  of  Beriini. 

The  Malpighian  bodies  are  found 

only  in  the  cortical  substance.     They 

are  small  round  bodies,  of  a  deep  red 

color,  and  of  the   average   diameter 

They   are   capsular   dilatations  of  the 


Longitudinal    section    of   the 


stitution  of  tlie  organ,  as  made 
up  of  distinct  lobules.—!.  Tlie 
flupra-renal  capsule.  2.  The  cor- 
tical portion  of  the  kidney.  3, 
3.  Its  medullary  portion,  consist- 
ing of  cones.  4,  4.  Two  of  the 
papilla;  projecting  iiito  their  cor- 
responding calyces.  5,5,  5.  The 
three  infundibula  ;  the  middle 
5  is  situated  in  the  mouth  of  a 
calyx.  6.  The  pelvis.  7.  The 
ureter. 

of  tJ^0  of  an  inch. 


KIDNEY  AND  ITS  SECRETION. 


257 


commencing  tubuli  uriniferi,  and  are  scattered  irregularly 
in  the  columns  of  Bertini,  but  regularly  arranged  in  double 
rows  in  the  cortical  arches.  Within  each  body  or  capsule  may 
be  observed  a  vascular  tuft  or  glomerulus,  which  consists  of 
the    ramifications   of  a  small  artery,  Fig.  84. 

the  afferent  vessel,  which,  after 
piercing  the  capsule,  divides  in  a 
radiated  manner  into  several 
branches,  which  ultimately  termi- 
nate in  a  finer  set  of  capillaries.  The 
blood  is  returned  from  these  by  a 
vein,  the  efferent  vessel,  which 
pierces  the  caspule  near  the  artery 
and  forms  a  venous  plexus  with 
other  efferent  vessels  around  the  ad-     pian  of  the  renai  circulation  in 

1  1     1      T /TT    r.j\    mi  1  man  and  Mammalia,    a,  Terml- 

iaCenttubuil(Jb  lg84}.  ine  capsules  are    nal  branch  of  the  artery,  giving 
..        ,,  ,  (>',iT  I'l      the  afferent  twig  1,  to  the  Mal- 

lined  by  a  layer  oi  epithelium,  which  pighian  tuft  m,  from   which 

,     , .  ,    ,  ,  ,  -  emerges  the   efferent  vessel,  2. 

13     believed    by  some  to  be    prolonged  other    efferent    vessels,    2,   are 

,        ,/•,/.  1  1  •!  1  seen  entering  the  plexus  of  ca- 

OVer  the  tuft  Ot  vessels  ;  while  others  plllarles,  surrounding  the  urini- 

-     ,  .     .  ,  ,  ,      .  ferous  tube,  t.  From  the  plexus 

are  ot    the  opinion     that    the    tuft    is  the  returning  vein,  y,  springs. 

wholly  uncovered.     The  tuft  in  the  frog,  and  other  reptiles 
is  covered   by   ciliated  epithelium. 

The  medullary  substance,  which  forms  about  one-fourth 
of  the  gland,  is  pale-red  in  color,  dense  in  texture,  and  pre- 
sents a  striated  appearance  on  account  of  the  number  of 
diverging  tubuli  uriniferi.  It  consists  of  conical  masses 
the  "  Malpighian  pyramids  ",  which  vary  in  number  from 
eight  to  eighteen,  their  bases  being  directed  towards  the 
circumference  of  the  organ,  and  their  apices  towards  the 
sinus,  in  which  they  terminate  by  smooth  rounded  extremi- 
ties, called  the  papillae  of  the  kidney.  The  conical  masses 
consist  of  the  tubuli  uriniferi,  blood-vessels,  nerves  and 
lymphatics,  held  together  by  areolar  tissue. 

The  tubuli  uririferi  commence  at  the  apices  of  the  cones 
by  small  openings :  as  they  pass  towards  the  base  they  divide 


'.4 
1 


2oS  SECRETING  GLANDS  AND  THEIR  SECRETIONS. 


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^'''-  '^•'^-  and  sub-divide,  and  diverge  un- 

til they  reach  the  cortical  sub 
stance,  when  they  become  con- 
voluted and  anastomose  freely 
with  each  other  and  terminate  in 
the  Malpighian  capsules.  There 
are  also  some  convoluted  tubes 
in  the  Malpighian  pyramids,  the 
loo'ped  tubes  of  Henle, wh\ch  de- 
scend to  a  certain  distance  in  the 
medullary  pyramid  and  return 
in  loops  to  rejoin  ohe  convoluted 
tubes.     The   diameter   of  these 

A.  Portion  ol  uriiiiferoiis  lubumasf-      loOpcd  tubcS  is  ahout  y-jrVlT  of  aU 
nified,    B.  Epithelial  cells  more  high-      .       r     /orv  \        rni,  t_ 

lymagiiifled  mch  (20   mmm).     ihe   number 

of  orifices  on  a  single  papilla  is  about  live  hundred.  The 
average  diameter  of  the  tubes  is  about  -j^ij-  of  an  inch  (50 
mmm)  and  they  consist  of  a  nearly  homogeneous  membrane 
lined  with  spheroidal  ephithelium  in  some  parts,and  cubical 
in  others.  Each  tube  as  it  passes  through  the  cortical  sub- 
stance, from  the  number  of  loops  which  surround  and  are 
connected  with  it,  presents  a  pyramidal  appearance ;  these 
are  called  the  "pyramids  ofFerrein,"  or  lobules  of  the  kid- 
ney.    The  total  number  of  tubes  is  about  two  millions. 

Arteries  and  Nerves. — The  kidney  is  supplied  by  the 
renal  artery,  which  divides  into  four  or  five  branches  as 
it  enters  the  hilum.  These  again  sub-divide  into  the  arie?'- 
iw  propria}  renales,  which  enter  the  kidney  in  the  spaces 
between  the  papilkie  (columns  of  Bertini^.  They  here  give 
off'  branches  which  supply  the  Malpighian  pyramids,  and 
cortical  substance.  Opposite  the  bases  of  these  pyramids 
they  make  an  abrupt  bend,  and  give  off  branches  (arteriolce 
rectoi)  which  supply  the  interior  of  the  pyramid,  descending 
to  the  apex.  They  are  then  continued  on  between  the 
"  lobules,"  or  pyramids  of  Ferrein,  under  the  name  of  inter- 
lobular branches,  until  they  reach  the  capsule.     In   their 


SECRETION  OF  URINE. 


250 


course  they  supply  the  Malpighian  bodies,  giving  them  tufts 
as  ah'eady  described  (Fig.  84).  The  afferent  vessel  after 
leaving  \he  Malpighian  body,  joins  the  capillary  plexus  sur- 
roundii.^  the  tubuli  uriniferi,  and  from  this  plexus  arise 
the  veins  which  return  the  blood.  The  circulation  in  the 
Malpighian  bodies  is  therefore  an  off-set  from  the  ordinary 
circulation,  and  in  this  respect  resembles  the  portal  cir- 
culation. The  nerves  of  the  kidney  are  derived  from  the 
solar  plexus,  the  semilunar  ganglia,  and  the  lesser  and 
smallest  splanchnic  nerves. 

Sinus  of  the  Kidney. — This  is  a  large  cavity  in  the 
interior  of  the  kidney  which  communicates  with  the  tubuli 
uriniferi  on  the  one  hand,  and  the  ureter  on  the  other.  It 
consists  of  three  prolongations,  the  infundibula,  one  situated 
at  each  extremity  of  the  organ,  and  one  in  the  middle.  Each 
infundibulum  is  divided  into  from  seven  to  thirteen  smaller 
portions,  the  calyces,  each  of  which  surrounds,  like  a  cup^ 
the  base  of  one  or  more  of  the  papillae.  It  is  lined  by 
spheroidal  epithelium. 

Secretion  of  Urine, — The  secretion  of  urine  from  the 
blood  is  effected  by  the  agency  of  cells.  Some  substances  as- 
urea,  uric  acid,  etc.,  exist  ready  formed  in  the  blood,  and 
need  only  to  be  removed ;  but  other  substances,  as  the  acid 
phosphates  and  the  sulphates  are  formed  by  the  agency  of 
cells.  It  is  probable,  also,  that  the  Malpighian  bodies  furnish 
chiefly  the  fluid  portion  of  the  urine,  for  it  has  been  observed 
that  in  those  animals  which  pass  the  urinary  excrement  in 
a  semi-solid  state,  the  tufts  of  the  Malpighian  bodies  are 
very  small.  The  secretion  of  urine  is  rapid,  in  com- 
parison with  other  secretions.  It  passes  down  the 
ureters  and  enters  the  bladder  drop  by  drop ;  this  may  be 
seen  in  some  cases  of  ectopia  vesica}.  Some  substances  pass 
very  rapidly  from  the  stomach  through  the  circulation,  to 
be  eliminated  by  the  kidney  ;  e.g ,  a  solution  of  potassium 
ferrocyanido  passed  in  one  minute,  while  some  vegetable 


•3 


f 

i 


260  SECRETING  GLANDS  AND  THEIR  SECRETIONS. 

substances  as  rhubarb,  occupied  from  sixteen  to  thirty-five 
minutes.  The  transit  is  slower,  when  the  substances  are 
taken  during  digestion. 


I. 


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ijli 


URINE. 

Healthy  urine  is  a  clear,  limpid  fluid,  of  a  pale  straw  or 
amber  color,  with  a  peculiar  odor,  and  saline  taste.  When 
first  voided,  it  has  an  acid  reaction,  but  after  a  short  time 
it  becomes  alkaline  from  the  development  of  ammonia 
■during  decomposition.  In  some  instances  the  urine  may 
become  turbid  on  cooling,  although  clear  and  transparent  at 
first.  The  specific  gravity  varies  from  1015  to  1025,  depend- 
ing on  the  time  at  which  it  is  secreted,  the  kind  of  food, 
drink,  etc.  In  consequence  of  this,  the  secretion  has  been 
divided  into  three  varieties : — 1st,  urina  potus,  or  that 
which  is  secreted  after  the  introduction  of  fluids  into  the 
body ;  2nd,  urina  cibi,  or  that  secreted  after  the  introduc- 
tion of  solid  food  ;  3rd,  urina  sanguinis,  or  that  secreted 
from  the  blood  when  neither  food  nor  drink  has  been  taken. 
For  purposes  of  investigation,  a  portion  of  the  urine  passed 
during  a  period  of  twenty-four  hours  should  be  taken.  In 
disease,  as  albuminuria,  the  specific  gravity  is  diminished 
to  100-i  ;  while  in  diabetes  it  may  be  increased  to  1050  or 
1060.  The  quantity  of  solids  in  any  given  specimen  of 
healthy  urine  may  be  determined  approximately  by 
doubling  the  last  two  figures  of  the  sp.  gr. ;  thus  1018, 
(18  X  2)  =36  grains  of  solids  in  1000  grains  of  the  urine. 
The  whole  quantity  of  urine  secreted  in  twenty-four  hours 
vai'ies,  according  to  the  amount  of  fluid  drank,  and  the 
quantity  secreted  by  the  skin,  from  thirty  to  fifty  ounces. 
The  secretion  of  the  skin  is  more  active  in  warm  weather 
than  in  cold,  and  consequently  the  quantity  of  urine  secreted 
during  winter  is  greater  than  in  summer. 

Chemical  Composition  of  the  Urine. — The  urine 
consists  of  water,  holding  in  solution  certain  animal  matters, 


CHEMICAL  COMPOSITION  OF  THE  URINE.      261 

salts,  coloring  matters,  etc.     Its  composition  according  to 
the  most  recent  analyses  is  as  follows,  in  1000  parts. 

Water 950.00 

Urea ii 26.20 

Uric  and  hippuric  acids,  combined  with   sodium,  potassium 

and  ammonium 2.15 

Creatine,  creatinine,  mucus  and  coloring  matter i  .22 

Sodium  and  potassium  chlorides 12.45 

Sodium  and  potassium  sulphates 3. 30 

Sodium,  potassium,  calcium  and  magnesium  phosphates   ...       4.28 
Sodium  bi-phosphate 40 

1000.00 

Water. — The  quantity  of  water  varies  in  different 
seasons,  and  according  to  the  drink,  exercise,  action  of  the 
skin,  etc.  In  some  diseases  it  is  very  much  increased,  as  in 
hysteria,  diabetes,  etc.  In  other  diseases,  as  albuminuria, 
diarrhoea  and  dysentery,  it  is  very  much  diminished.  In 
fevers,  albuminuria,  and  in  inflammation  also,  the  quantity 
of  water  is  almost  invariabl}'^  diminished. 

Urea. — (C  H4  N2  O).  This  constitutes  more  than  half  of 
the  solid  ma;tter  of  healthy  urine.  The  quantity  is  in- 
creased by  a  purely  animal  or  highly  nitrogenous  diet,  and 
slightly  by  exercise.  The  increase  of  urea  in  active 
muscular  exercise  was  formerly  supposed  to  be  in  exact 
proportion  to  the  amount  of  muscular  exercise,  but  this  has 
been  found  by  experiment  not  to  be  the  case  ;  the  waste 
of  muscle  cannot  be  expressed  by  the  increase  in  urea. 
Urea  exists  already  formed  in  the  blood,  and  is  simply  re- 
moved by  the  kidneys.  It  is  formed  from  the  decomposition 
of  the  nitrogenous  elements  of  the  food,  and  from  the 
disintegration  of  the  azotized  tissues.  It  may  be  readily 
obtained  by  evaporating  urine  to  the  consistence  of  honey, 
and  acting  on  it  with  four  parts  of  alcohol ;  then  evaporating 
and  crystallizing.  It  crystallizes  in  acicular  crystals,  which 
appear,  under  the  microscope,  as  four-sided  prisms,  (Fig.  86). 
It  is  purified  by  filtering  through  animal  charcoal.  It 
may  also  be  obtained  in  the  form  of  urea  nitrate  (C  H*  N2 
O  H  N  O3 ),  by  evaporating  urine  to  one-half,  and  then  adding 


•3 
1 

i 


262  SECRETING  GLANDS  AND  THEIR  SECRETIONS. 


c 
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I. 

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an  equal  quantity  of  nitric  acid,  and  crystallizing.     Urea 
I'lg's  sojuiii^HT.  jg  identical  in  composition  witli 

ammonium  isocyanate,  (N  H4  C 
NO=C  H4  N2  0),  and  may  be 
prepared  artificially  by  the 
chemist,  by  double  decompo- 
sition from  potassium  isocy- 
anate, and  ammonium  sulph- 
ate. Urea  is  colorless  when 
pure,  and  destitute  of  smell, 
neutral  in  its  reaction  to  test 
cr5ais°of  urlf^ita:'  """  "''•  ''•  paper,  and  soluble  in  water 
and  alcohol.  When  urine  stands  for  some  time,  the  urea 
is  decomposed,  and  forms  ammonium  carbonate.  It  is  also 
decomposed,  in  some  cases,  before  it  leaves  the  bladder,  as 
in  paralysis,  and  some  low  forms  of  disease.  An  average  of 
500  grains  (32.4  grammes)  of  urea  are  excreted  from  the  body 
in  twenty-four  hours,  when  the  kidney  is  in  a  healthy  con- 
dition ;  but  in  some  diseases,  as,  e.  g.,  in  desquamative 
nephritis,  Bright's  disease,  or  congestion  of  the  kidney  from 
any  cause,  a  certain  portion  of  the  urea  is  kept  back,  and 
circulating  through  the  system  may,  by  its  poisonous  effects 
on  the  cells,  give  rise  to  dropsies  in  different  parts  of  the 
body,  or  from  its  deleterious  effects  on  the  nervous  system, 
occasion  uraeraic  convulsions  and  coma. 

Uric  or  Lithic  Acid  (C5  H4  N4  O3 ). — This  substance  is 
rarely  absent  from  healthy  urine.  It  is  combined  with 
sodium  and  ammonium  in  the  form  cf  urates.  It  predomi- 
nates in  the  urinary  excrements  of  birds,  serpents,  and 
other  reptiles  ;  while  urea  predominates  in  the  mammalia, 
especially  the  herhivora.  In  the  urine  of  the  feline  tribe, 
uric  acid  is  sometimes  entirely  replaced  by  urea.  Uric  acid 
and  urea  are,  therefore,  closely  allied  to  each  other,  and 
each  alone  may  represent  the  excretion  of  the  two.  The 
quantity  of  uiic  acid,  like  that  of  urea,  is  increased  by  the 
use  of  animal  or  highly  niti'ogenized  food,  and  decreased  by 


HIPP  URIC  ACID. 


263 


food  which  is  free  from  nitrogen.  It  is  increased  in  all 
febrile  conditions,  and  in  gout  it  is  deposited  in  and  around 
joints,  in  the  form  of  sodium  urate,  and  constitutes  the  so- 
called  "chalk-stones."  Uric  acid  has  been  detected  in 
the  blood  of  healthy  persons,  and  in  considerable  quantity 
in  gouty  patients.  It  is  supposed  to  be  formed  in  the  sys- 
tem from  the  disintegration  of  the  azotized  tissues.  Uric 
acid  may  be  readily  obtained  by  adding  a  few  drops  of 
hydrochloric  acid  to  a  portion  of  urine  in  a  watch  glass ; 
after  a  few  hours  it  is  found  crystallized  on  the  sides  and 
bottom  of  the  vessel.  In  larger  quantities  it  may  be 
obtained  from  the  thick,  white,  urinaiy  excrement  of  ser- 
pents or  birds,  which  consists  almost  entirely  of  ammonium 
urate.  This  substance  is  dissolved  in  warm  water,  and  then 
decomposed  by  nitric  or  hydrochloric  acid.  The  crystals  of 
uric  acid  assume  very  various  and  somewhat  fantastic 
shapes,  most  frequently  rhombic  or  diamond  shaped  (Fig. 
87).  It  is  insoluble  in  alcohol  and  ether.  When  the  urates 
are  in  excess  in  the  urine,  they  appear  as  a  "  brick-dust " 
sediment  in  the  vessel.  They  may  be  distinguished  from 
other  deposits  by  their  not  appearing  until  the  urine 
becomes  cold,  and  by  disappearing  again  entirely  on  the 
application  of  heat. 

HiPPURic  Acid  (Co  Hq  NO3  .) — This  acid  exists  in  small 
quantity  in  human  urine,  pro- 
bably in  the  form  of  sodium 
and  ])otassium  hippurates,  but 
is  very  abundant  in  the  urine 
of  cows,  horses  and  other  her- 
bivorous animals.  It  is  closely 
allied  to  benzoic  acid  (C7  He  O2  ), 
and  this  substance  when  taken 
into  the  system,  is  excreted  in 
the  form  of  hippuric  acid.  Hip- 
puric  acid  is  chiefly  formed  fi-om  8o^'S''S!a^c"S^;«^^ftS 
vegetable  articles  of  food,  and    l^ta^ol'Zniunrur^t" ""' ^""'^ 


Fig's  88  ami  W). 


2G4'  SECRETING  GLANDS  AND  THEIR  SECRETIONS. 


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may  be  prepared  from  the  urine  of  cows  by  precipitation 
with  liydrochloric  acid.  It  has  a  bitter  taste,  is  slightly 
soluble  in  cold,  but  very  soluble  in  hot  water  and  alcohol. 

Greativ.e — (C4  H9  N.,  O2  )  occurs  in  very  small  quantity 
in  the  urine.  It  is  a  colorless  crystalline  body,  with  a  pun- 
gent taste,  soluble  in  water,  but  almost  insoluble  in  alcohol. 
It  may  be  obtained  I'rom  the  flesh  of  animals.  It  is  most 
abundant  in  the  fle.sh  of  fowls,  and  in  the  heart  of  the  ox. 

Creatinine — (O4  H7  Na  O)  is  also  found  in  the  urine.  It 
crystallizes  in  colorless  crystals,  has  a  hot,  pungent  taste  like 
caustic  ammonia,  and  is  soluble  in  water  and  alcohol.  It 
may  be  formed  from  creatine,  by  the  action  of  hydrochloric 
acid,  and  is  probably  formed   from  creatine  in  the  .system. 

Urochrome  or  Urosacine,  the  coloring  matter  of  the 
urine,  has  been  already  described,  (see  proximate  prin- 
ciples). A  substance  termed  Indican  has  been  found  in  the 
urine  by  several  observers;  by  its  decomposition  indigo  blue, 
and  indigo  red  are  produced. 

The  urine  also  contains  a  certain  amount  of  mucus  and 
epithelial  debris  from  the  mucous  surface  of  the  urinary 

])assages. 

Salts. — The  salts  of  the  urine  constitute  less  than  half  of 
the  solid  ingredients.  Sodium  and  potassium  chlo»ides  form 
a  large  proportion  of  the  salines  of  the  urine,  the  former 
being  more  abundant  than  the  latter.  They  are  derived  iu 
part  from  the  food,  and  also  partly  from  chemical  decom- 
position within  the  body.  They  may  be  readily  precipitated 
by  a  solution  of  silver  nitrate  after  the  urine  has  been 
acidulated  by  nitric  acid.  When  silver  nitrate  is  added 
to  healthy  urine,  a  whitish  precipitate  o*  silver  chloride 
and  sodium  phosphate  is  thrown  down;  the  latter  may  be 
dissolved  by  the  addition  of  a  little  nitric  acid.  The  silver 
chloride  is  readily  dissolved  by  a  little  ammonia. 

The  sulphates  are  more  abundant  in  the  urine,  than  in  the 


THE  PHOSPHA  TES. 


2G5 


fluids  and  tissues  of  the  body.  They  are  increased  by  ex- 
ercise, and  in  diseases  accompanied  by  muscular  exertion, 
as  in  chorea  and  delirium  tremens.  They  are  also  increased 
by  the  introduction  of  sulphur  or  the  sulphides  into  the 
system.  The  sulphuric  acid  is  formed  by  the  oxidation  of 
sulphur,  which  is  derived  from  the  decomposing  albuminoid 
substances. 

The  phosphates  are  more  numerous  than  the  sulphates. 
Phosphorus  is  derived  from  the  decomposition  of  nerve  sub- 
stance, albumen  and  fibrin,  and  like  sulphur,  is  oxidized  at 
the  lungs,  and  then  unites  with  the  bases  to  form  salts.  The 
alkaline  jihosp hates, or  potassium  and  sodium  phosphates  aro 
those  salts  by  which  most  of  the  phosphoric  acid  is  elimi- 
nated in  the  urine.  They  are  readily  soluble,  and  never 
appear  as  a  precipitate  in  urine.  The  quantity  of  alkalin© 
phosphates  is  increased  by  a  diet  of  animal  food  :  also  by 
great  mental  exertion,  and  in  phrenitis.  They  arc  also  in- 
creased by  exercise,  while  the  earthy  are  diminished.  The 
earthy  phosphates,  or  calcium  and  magnesium  phosphates, 
are  not  very  abundant  in  the  urine.  They  are  held  in  solu- 
tion by  the  sodium  biphosphate,  and  when  this  is  absent  or 
neutralized  they  fall  as  a  precipitate. 

The  acid  sodium  phosphate,  or  sodium  biphosi)hate  gives 
the  urine  its  acid  reaction.  It  is  supposed  to  be  formed 
from  the  ordinary  sodium  phosphate  of  the  blood  by  the 
action  of  uric  acid,  which  unites  with  a  part  of  the  sodium 
forming  sodium  urate,  leaving  an  acid  sodium  j^hosphate. 
Though  freshly  voided  urine  exhibits  an  acid  reaction,  yet- 
it  has  no  free  acid,  but  within  a  few  hours  after  its  discharge 
it  undergoes  the  so-called  acid  fermentation  resulting  in  the 
production  of  free  lactic,  and  sometimes  oxalic  acid,  formed 
from  some  of  the  organic  ingredients.  The  latter  when 
formed  is  precipitated  with  calcium,  forming  a  sediment  of 
calcium  oxalate  (Fig.  90).      In  a  few  days  these  changes- 


I 
•» 
1 

t 

i 


•266  SECRETING  GLANDS  AND  THEIR  SECRETIONS. 


c 
c 


I. 


f 

Sh.'' 


Fi,'H.<.oan.ini.  ^^^^^^  ^^^^  ^^.^  followed  by  the 

so-callod  (dhdine  fermc/niation, 
(luring  which  some  of  the  phos- 
phates are  thrown  down.  This 
change  is  brought  about  by  the 
decomposition  of  urea  and  its 
transformation  into  ammonium 
carbonate.  This  causes  a  pre- 
c'ii»itation  of  the  earthy  phos- 
phates which  unite  with  some 

Kitf.   ))0    Crystals   of  uakiiim  oxulttte-     ,  n    ii  ,     „  .^,.^«,^:,,.v.     o«,1     olq    Aa 

I'ijf. 01  crystilH of  cystin.  ot  the  ammoniuui,  and  aie  ue- 

])osited  in  the  form  of  ammonio-magnesiuin  phosphate  (triple 
phosphate)  Fig.  89.  The  urine  at  this  time  has  a  strongly 
ammoniacal  odor.  Cystin  (Fig.  91),  is  occasionally  found 
in  unhealthy  urine. 

MAMMARY   GLANDS   AND  THEIR  SECRETION. 

These  are  the  organs  which  secrete  the  milk.  They  are 
large  and  hemispherical  in  the  female,  but  are  quite  rudi- 
mentary in  the  male.  They  are  situated  in  front  of  the 
pectoralis  major,  between  the  third  and  sixth  ribs,  and  ex- 
tend from  the  sides  of  the  sternum  nearly  to  the  axilhe. 
They  are  enlarged  at  puberty,  increased  during  pregnancy 
and  lactation,  and  diminished  in  old  age.  The  outer  surface 
of  the  mamma  presents  a  little  be^.ow  the  centre,  a  small 
conical  eminence — the  nipple — the  surface  of  which  is  dark- 
colored,  and  surrounded  by  an  areola,  which  has  a  rosy  hue 
in  the  virgin,  but  becomes  very  dark-colored  during  preg- 
nancy. Its  summit  is  perforated  by  numerous  openings, 
the  orifices  of  the  lactiferous  ducts.  It  is  also  provided 
with  a  number  of  .sebaceous  glands,  situated  near  its  base 
and  upon  the  surface  of  the  areola,  which  secrete  a  peculiar 
fatty  rubstance  for  the  protection  of  the  nipple  during  suck- 
ing. The  nipple  consists  of  numerous  blood-vessels,  nerves, 
lymphatics,  ducts,  erectile  tissue,  and  nonstriated  muscular 
fibre-cells,  and  is  capable  of  slight  erection  during  sexual  ex- 
citement or  irritation. 


MILK.  267 

Structure. — The  mamma  consists  of  numerous  lobes, 
which  are  made  up  of  small  lobules,  connected  together  by 
areolar  tissue,  blood-vessels  and  ducts.  There  is  also  some 
adipose  tissue  between  the  lobules.  Each  lobule,  which  is 
a  representation  of  the  whole  gland,  consists  of  a  cluster  of 
rounded  vesicles,  which  open  into  the  smallest  branches  of 
the  lactiferous  ducts,  and  these,  uniting,  form  larger  ducts 
— the  tubuli  lactiferi.  These  vary  in  number  from  fifteen 
to  twenty,  and  converge  towards  the  areola,  beneath  which 
they  form  dilatations,  ov  ampulloi,  which  serve  as  reservoirs 
for  the  milk ;  they  then  become  contracted,  and  continue 
onwards  to  the  summit  of  the  nipple,  where  they  open  by 
separate  orifices,  which  are  narrower  than  the  ducts  them- 
selves. The  entire  surface  of  the  gland  is  invested  by 
fibrous  tissue,  from  which  numerous  septa  are  derived,  which 
])ass  between  the  lobes. 

Milk. — The  secretion  of  milk  is  usually  limited  to  the 
period  succeeding  parturition,  yet  this  is  not  invariably  the 
case.  Numerous  instances  are  on  record  where  young 
women  who  have  never  borne  children,  and  even  old 
women,  have  been  able  to  act  as  wet  nurses.  In  some  rare 
cavses,  the  male  has  been  known  to  secrete  milk  in  the 
breasts.  A  fluid  resembling  milk,  may  frequently  be  ex- 
pressed from  the  mammary  glands  of  infants.  Milk  has 
an  alkaline  reaction,  and  the  specific  gravity  varies  from 
1020  to  1030.  The  specific  gravity  alone  is  of  no  value  as 
an  indication  of  the  richness  of  the  milk.  The  average 
chemical  composition  of  human  milk  is  as  follows,  in  1000 
1  tarts  : 

Water 890 

Butter 26 

Casein  andExtractive 40 

Lactose 42 

Fixed  Salts 2 

1000 

When  milk  is  examined  with  a  microscope,  a  large  number 
of  minute  particles  may  be   seen,  termed  "  milk  globules," 
1.5 


268  SECRETING  GLANDS  AND  THEIR  SECRETIONS. 


c 


r 


IL 


|«ni 

tor 

EH.!  , 


which  vary  in  size  from  5„'oo  to  xsAao  of  an  inch  (8.3  to  2 
muiin)    in    diameter.     Tliey   are   coated  with   albuminous 

V\k.  02.  Fijf.  03. 


Oil  ^lohitlcsof  liunian  milk.  Oil  (^lobules   of  cow's  mill<. 

matter,  and  are  sohil)le  in  ether  and  alkalies.  In  the 
colostruTn,  or  first  milk  secreted  after  labor,  large,  yellow, 
granulated  bodies  may  be  seen,  called  colostram  corpuscles. 
Theyare  supposed  by  some  to  be  exudation  corpuscles;  others 
regard  them  as  transformations  of  the  epithelial  cells  of  the 
gland,  containing  fatty  matter.  The  colostrum  has  a  pur- 
gative effect  on  the  chiM,  which  is  useful  in  clearing  the 
bowels  of  the  meconium  which  they  contain  at  birth.  The 
oleaginous  matter  of  milk  chiefly  consists  of  the  ordinary 
constituents  of  fat,  together  with  a  substance  called  "butyrin," 
to  which  the  taste  and  smell  of  butter  are  due.  When  this 
substance  is  treated  with  alkalies,  or  suffers  decomposition, 
the  following  volatile  acids  are  produced,  viz.  ;  butyric, 
caproic,  caprylic,  and  capric  (rutic.)  These  are  called  butter 
acids. 

The  casein  of  human  milk  is  not  so  readily  precipitated 
as  cow's  milk.  It  requires  a  large  amount  of  acid,  and  rennet 
does  not  seem  to  take  effect  upon  it,  unless  an  acid  be 
present.  The  casein  of  asses'  milk  boars  a  closei  resemblance 
to  that  of  human  milk,  than  does  that  of  the  cow.  The 
best  substitute  for  hinnan  milk,  however,  is  cow's  milk 
diluted  with  water,  and  a  little  sugar  added. 

Lactose  or  milk  sugar  (C12  H24  O12),  may  be  obtained  from 
whey  by  evaporation  and  crystallization.  It  strongly  re- 
sembles glucose,  into    vvhich  it  niay  be  converted    by  the 

drochloric  acid.    The  action 


'P 


hyi 


of  a  fennent  causes  lactose  to  undergo  the  lactic  acid  fer- 


MILK. 


msi 


mentation;  and  wlien  lactic  acitl,  or  .calcium  lactate  is 
allowed  to  stand  for  some  time,  it  is  changed  into  Imtyric 
acid,  or  calcium  butyrate,  having  undergone  tin;  "  luitj-ric 
acid  fermentation." 

The  saline  matter  of  the  milk  is  nearly  identical  with  that 
of  the  blood,  with  an  increase  in  the  calcium  and  magncsitnn 
phosphates.  From  what  has  been  already  stated,  it  will  be 
observed  that  milk  contains  the  four  classes  of  ])iinciples 
which  are  i-equired  for  human  food,  viz:  The  aqueous,  the 
aU)mninous, the  oleafjuwus^ixud  the  scw)c//arme,conse(iuently 
it  is  well  adapted  to  the  nourishment  of  the  young  animal. 
From  20  to  40  ounc(^s  of  milk  are  secreted  in  24  hours. 
Stimulating  li(juors  often  used  to  incre  se  the  quantity  of 
milk,  seldom  act  otherwise  than  prejudicial. 

Certain  inedicinal  agents,  when  administei'ed  to  the 
mother,  may  pass  into  the  milk,  and  in  this  way  ati'fct  the 
child.  As  a  rule,  salines  pass  more  readily  than  vegetalde 
substances.  Medicine  may  be  administered  to  the  mother, 
instead  of  the  child,  when  it  is  desired  to  act  upon  the  latter. 

Eniotious  of  the  niiud,  as  anger,  gi'ief,  fear,  etc.,  ])ro- 
duce  peculiar  changes  in  the  quantity  and  quality  of  the 
milk;  for  example,  anger  produces  very  irritating  milk,  which 
cap  es  gi'iping  ii^i  the  child,  and  green  stools.  Grief 
diminishes  the  secretion,  and  frequently  vitiates  it.  Fear 
also  diminishes  the  secretion,  and  that  which  is  secreted 
under  such  circumstanees  is  highly  irritating.  Violent  ex- 
ercise, or  great  anxiety  of  mind,  has  also  a  bad  effect  on  the 
secretion  of  milk.  Cases  are  recorded  in  wliicli  children 
have  had  convulsions,  and  died  shortly  after  sucking  milk 
secreted  un'''3r  the  foregoing  circumstances. 


270 


DUCTLESS  OR  VASCULAR  GLANDS. 


CHAPTER  XII. 


c 
c 

c. 
I. 

Ih 

rat 
I 

c 

r 

Ml 

It' 

Onr-, 

cu 
ciu  , . 

'■"Jtt-'ik, ,-, 


DUCTLESS   OR  VASCULAR  GLANDS. 

These  are  so  named  from  havinf,'  no  excretory  ducts  ; 
they  are  the  spleen,  supra-renal  capsules,  thymus  and  thy- 
roid glands.  They  contain  the  same  essential  structures  as 
the  secreting  glands,  except  the  ducts.  They  are  highly 
vascular,  and  are  concerned  in  the  elaboration  of  the  blood. 
Their  function,  however,  does  not  seem  essential  to  life. 
They  may  become  atrophied,  or  be  removed  from  animals, 
without  any  serious  consequences. 

SPLEEN.   . 

t 

The  spleen  is  situated  in  the  left  hypochondriac  region, 
embracing  the  cardiac  end  of  the  stomach.  It  is  of  an 
oblong  shape,  highly  vascular,  very  brittle,  and  of  a  bluish- 
red  color.  It  measures  five  inches  in  length,  three  or  four 
in  breadth,  and  one  and  a  half  in  thickness,  and  weighs  from 
four  to  six  ounces. 

Structure. — It  is  invested  by  two  coats,  an  external 
serous  and  an  internal  fibrous  elastic  coat.  The  serous  coat 
is  derived  from  the  peritoneum,  and  is  intimately  adherent 
to  the  fibrous  coat.  It  covers  nearly  the  whole  organ,  being 
reflected  from  it  at  the  upper  end  on  to  the  diaphragm  form- 
ing the  suspensory  ligament,  and  at  the  hilum  on  to  the 
great  end  of  the  stomach,  forming  the  gastro-splenic  omen- 
tum. Thejibrous  coat  consists  of  white  fibrous  and  yellow 
elastic  tissue.  It  covers  the  exterior  of  the  organ,  and  sends 
prolongations  inwards  at  the  hilum,  in  the  form  of  vagina? 
or  sheaths,  which  surround  the  vessels.  From  these  sheaths, 
and  from  the  inner  surface  of  the  fibrous  coat,  numerous  tra- 
beculse  or  bands  pass  in  all  directions,   and   these   uniting 


STRUCTURE  OF  THE  SPLEEN. 


271 


bemg 
bim- 
o  the 
)men- 
ellow 
sends 
aijina3 
eaths, 
js  tra- 


form  the  areolar  framework  of  the  spleen.  The  presence  of 
the  elastic  tissue,  permits  of  the  great  enlargement  of  this 
organ  which  is  sometimes  seen.  The  spaces  or  areolae  be- 
tween the  bands  are  filled  with  a  soft  pulpy  mass,  of  a  dark 
reddish-brown  color,  consisting  of  colorless  and  colored  ele- 
ments— the  proper  substance  of  the  spleen,  or  spleen  iTuXp — 
and  some  rounded  bodies  the  Malpighian  corpuscles. 

The  colorless  elements  form  about  one-half  or  two-thirds 
of  the  entire  pulp,  especially  in  well-fed  animals,  and  consist 
of  granular  plasma,  free  nuclei,  about  the  size  of  red  blood 
corpuscles,  and  a  few  nucleated  lymphoid  cells.  The  colored 
elements  consist  of  unchanged  red  blood  corpuscles,  and 
blood  discs  in  various  stages  of  decay.  Besides  these,  may 
be  seen  a  number  of  granular  bodies  or  crystals,  which  in 
chemical  composition  resemble  the  coloring  matter  of  the 
blood. 

The  Malpi(jhiaii  corpuscles  are  rounded  bodies  from  ,?(, 
to  a'j  of  an  inch  (.8  to  .4-  mm)  in  diameter,  of  a  semi-opaque 
whitish  color,  and  are  more  distinct  in  early  life  than  in 
'•''^-"  adult  age.      Each  con- 

sists of  a  membranous 
capsule,homogeneous  in 
structure,  and  formed 
by  a  prolongation  from 
the  sheath  of  the  small 
arteries  to  which  it  is 
attached.  They  are  sur- 
rounded and  embraced 
by  the  radicles  of  the 
arteries,  and  present  a 
resemblance  to  the  buds 
of  the  moss  rose.  Each 
showing  the  Mai-  ^^^^^^^  contains  a  soft 

white  sul)stance,  consisting  of  granular  ])lasma,  nuclei,  an  I 
nucleated  13'mphoid  cells  similar   to  the  colorless  elements 


Branch  of  the  splenic  artery, 
pighi:iii  oorpnaoles. 


272 


DUCTLESS  OR  VASCULAR  GLANDS. 


c 
c 

c 
I. 
I- 

»i 

m\ 

I 

f 

c 
c 

•^';, 

•w' 
•»f  ■ 

oa 

tn.1  I 


of  the  pulp.     Small  capillaries  pass  into  their  interior  and 
form  a  minute  plexus. 

The  splenic  artery  is  large  in  proportion  to  the 
size  of  the  gland,  tortuous  in  its  course,  and  divides  into 
from  four  to  six  branches,  which  enter  the  hilum. 
Each  branch  runs  transversely  from  within  outwards,  and 
divides  into  smaller  branches  ;  these  ultimately  terminate 
in  tufts  or  pencils,  which  lie  in  contact  with  the  pulp.  The 
most  striking  peculiarity  is,  that  each  of  the  larger  branches 
supplies  chiefly  that  part  of  the  organ  to  which  It  is  dis- 
tributed, having  no  anastomosis  with  the  adjoining  branches. 
The  cajsiZ^aries terminate  either  directly  inthe  veins,  or  open 
into  csecal  or  lacunar  spaces,  from  which  the  veins  arise.  The 
veins  arise  either  in  the  ordinary  way  from  the  capillaries 
or  by  communicating  intercellular  spaces,  or  distinct  csecal 
pouches.  They  are  much  larger  and  more  numerous  than 
the  arteries,  and  by  their  junction  form  from  four  to  six 
branches  which  emerge  at  the  hilum,  and  uniting  form  the 
splenic  vein,  the  largest  branch  of  the  portal.  From  this  it 
will  be  seen  that  the  blood  returning  from  the  spleen  passes 
through  the  liver  before  it  enters  the  general  circulation. 

Function  of  the  Spleen. — In  consequence  of  the  vas- 
cular arrangement  and  the  large  amount  of  elastic  tissue 
which  this  organ  contains,  it  is  liable  to  undergo  great 
changes  in  volume.  Enlargement  of  the  spleen  is  apt 
to  occur  from  internal  venous  congestion,  such  as  occurs  in 
the  cold  stage  of  intermittent  fever.  When  intermittent 
fever  is  long-continued,  the  spleen  is  generally  very  much 
enlarged,  constituting  what  is  commonly  called  "  ague 
cake." 

It  was  formerly  supposed  to  act  as  a  diverticulum  of  the 
liver,  relieving  its  vessels  from  undue  turgescence  and  pre- 
venting congestion  of  the  liver,  stomach  and  bowels  ;  and  also 
that  it  promoted  the  disintegration  of  the  red  blood 
corpuscles ;  but  these  views  cannot  be  accepted  in 
the    present    state    of    our    knowledge.      The    spleen    is 


SUPRA-RENAL  CAPSULES. 


273 


larger  four  or  five  hours  after  food  is  taken,  and 
contains  a  larger  proportion  of  finely  granular  albu- 
minous material,  than  at  any  other  time,  therefore  it  is 
supposed  that  this  organ  is  the  receptacle  for  the  increased 
quantity  of  albuminous  material  of  the  food,  and  which  can- 
not be  admitted  into  the  system  generally,  without  danger, 
until  the  volume  of  the  circulating  fluid  has  been  reduced 
by  secretion.  In  support  of  this  theory,  it  has  been  stated 
that  animals  from  which  the  spleen  has  been  removed,  are 
very  liable  to  die  of  apoplexy,  after  taking  large  quantities 
of  food.  It  would  therefore  appear  to  be  a  storehouse  of 
nutrient  material,  which  may  be  drawn  upon  as  the  system 
requires.  The  increase  of  the  fibrin  in  the  splenic  vein 
would  show  that  the  nutrient  material  is  elaborated  during 
its  withdrawal.  It  is  also  supposed  to  form  the  germs  of 
future  blood  corpuscles,  as  there  is  found  to  be  a  large  in- 
crease of  the  colorless  corpuscles  in  the  blood  of  the  splenic 
vein. 

SUPJIA-RENAL  CAPSULES. 

The  supra-renal  capsules  are  situated  one  upon  the  upper 
extremity  of  each  kidney,  somewhat  triangular  in  shape,  the 
base  being  applied  to  the  kidney,  and  the  apex  directed  up- 
wards. Each  gland  is  about  one  and  one-half  to  two  inches 
in  length,  rather  less  in  width,  about  one-fourth  of  an  inch 
in  thickness,  and  weighs  from  one  to  two  drachms. 

Structure. — Like  the  kidneys,  they  are  divided  into  a 
cortical  and  medullary  portion.  The  cortical  portion, 
which  forms  the  principal  part  of  the  organ,  ia  of  a  deep  yel- 
low color,  and  consists  of  narrow,  columnar  masses,  arranged 
perpendicularly  to  the  surface,  and  held  together  by  areolar 
tissue.  These  columnar  masses  measure  about  ij-j^j  of  an 
inch  (35  mmm)  in  diameter,  and  consist  of  oval  spaces  or 
parallel  tubes,  containing  a  finely  granular  plasma,  a  mass 
of  nucleated  cells  with  large  nuclei,  and  oil  globules.  The 
medullary  substance  consists  of  areolar  tissue,  containing  a 


.1 


c 
c 

E 

h 

m 


•*^v 


CCC: 


274 


DUCTLESS  OR  VASCULAR  GLANDS. 


plexus  of  minute  veins,  having  stellate  or  polygonal  granu- 
lar cells  in  its  meshes.  It  is  soft  and  pulpy,  very  dark  in 
color,  hence  the  name  atrahiliary  substance,  sometimes 
given  to  ib.  These  glands  are  more  highly  supplied  with 
nerves  than  any  other  glands  in  the  body. 

Function. — Very  little  is  known  regarding  their  function. 
They  were  formerly  supposed  to  be  the  diverticula  of  the 
kidney.  They  are  probably  concerned  in  elaborating  some 
of  the  materials  of  the  blood.  They  are  developed  at  an 
early  period  in  foetal  life,  and  are  larger  than  the  kidneys  ; 
but  afterwards  relatively  diminish.  It  was  observed  by 
Addison  that  disease  of  the  supra-renal  capsules  was  asso- 
ciated with  anemia,  general  weakness,  and  a  peculiar  change 
of  color  in  the  skin,  the  patient  resembling  a  mulatto.  The 
disease  is  called  morbus  Addisonii. 

THYMUS  GLAND. 

This  is  only  a  temporary  organ.  It  reaches  its  largest 
size  at  the  end  of  the  second  year,  and  then  declines  until 
puberty,  when  only  a  small  part  remains.  It  is  situated 
partly  in  the  anterior  mediastinum,  and  partly  in  the  neck, 
extending  from  the  lower  border  of  the  thyroid  gland  to 
the  fourth  costal  cartilage.  It  is  somewhat  oval  in  shape, 
of  a  pinkish  grey  color,  lobulated  on  its  surface,  and  consists 
of  two  lobes,  [t  is  about  two  inches  in  length,  one  and 
a  half  in  breadth,  three  or  four  lines  in  thickness,  and 
weighs  about  half  an  ounce. 

Structure, — Each  lobe  consists  of  a  central  cavity  or 
reservoir,  around  which  are  arranged  numerous  lobules,  held 
together  by  delicate  areolar  tissue.  The  lobules  vary  in 
size  from  a  pin's  head  to  a  pea,  and  each  contains  a  smf».ll 
cavity  from  ^^  to  -^^  of  an  inch  (1.4  to  .5  mm)  in  diameter, 
which  communicates  with  the  central  cavity  or  reservoir  of 
the  organ.  Each  lobule  is  surrounded  by  smaller  or  second- 
ary lobules  or  acini,  the  cavities  of  which  communicate  with 
those  of  the  primary  lobules.     If  the   capsule  and   areolar 


THYROID  GLAND. 


275 


tissue  holding  the  parts  together  be  dissected  off,  the  gland 
may  be  drawn  out  into  a  tubular  cord,  around  which  the 
lobules  are  arranged  in  a  spiral  manner.  The  closed  cavity 
of  the  organ,  and  the  secondary  lobules  or  acini  contain  a 
.chyle-like  fluid,  consisting  of  nucleated  corpuscles,  granular 
nuclei  and  lymphoid  cells. 

Function. — This  organ  would  appear  to  be  connected 
with  the  preparation  of  matter  for  the  pulmonary  arteries 
in  early  life.  In  ill-nourished  children  the  corpuscles  be- 
come filled  with  fat,  which  is  supposed  to  be  added  to  the 
blood. 


ity  or 
held 

rv   in 


THYROID  GLAND. 

The  thyroid  gland  is  situated  at  the  upper  part  of  the 
trachea,  and  consists  of  two  lobes  connected  by  a  narrow 
band  (the  isthmus),  which  crosses  the  second  and  third 
rings.  Each  lobe  is  conical  in  shape,  about  two  inches  in 
length,  and  three-quarters  of  an  inch  in  breadth,  the  right 
being  the  larger.  The  whole  gland  weighs  from  one  to  tw» 
ounces.  It  is  of  a  brownish-red  color,  larger  in  females  than 
in  males,  and  is  increased  during  menstruation.  It  is  oc- 
casionally very  much  hypertrophied,  and  c^^nstitutes  hron- 
chocele  or  goitre.  In  some  countries,  as  in  Switzerland  and 
Northern  Italy,  bronchocele  is  very  prevalent  in  both  sexes. 
The  children  of  goitrous  parents  are  dwarfish,  very  defective 
in  mental  and  moral  faculties,  and  are  known  as  cyetiiis. 

Structure. — In  structure  it  consists  of  lobules,  held  to- 
gether by  areolar  tissue.  Each  lobule  consists  of  a  number 
of  closed  vesicles,  oblong  or  spherical  in  shape,  each  contain- 
ing an  albuminoid  plasma,  consisting  of  granules,  oil  glo- 
bules, nuclei,  and  nucleated  cells,  the  latter  occupying  the 
position  of  an  epithelium  within  the  vesicles.  There  is  also 
some  colloid  substance,  which  is  most  abundant  in  enlarge- 
ment of  the  gland.  The  vesicles  vary  in  size  from  ^^  to  to\5w 
of  an  inch  (300  to  12  mmm)  in  diameter. 


276 


THE  NERVOUS  SYSTEM. 


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Function. — The  thyroid  gland  is  supposed  by  some  to  act 
as  a  diverticulum  of  the  cerebral  circulation.  When  the  brain 
is  inactive,  the  thyroid  gland  takes  on  an  increased  action, 
and  accommodates  the  blood  that  would  otherwise  go  to 
that  organ.  This  view  is  based  on  the  fact  that  the  arteries 
which  supply  this  gland  arise  in  close  proximity  to  those 
which  supply  the  brain.  The  vesicles  also  probably  removes, 
and  store  up  from  the  blood,  certain  constituents  which  are 
not  required  in  its  passive  state,  to  be  returned  to  it  when 
it  resumes  its  activity. 


CHAPTER  XIIL 


THE   NERVOUS   SYSTEM. 

The  nervous  system  consists  of  two  portions,  the 
cerebrospinal,  and  the  sympathetic  or  ganglionic  system. 
The  former  was  distinguished  by  Bichat  as  the  nervous 
system  of  animal  life ;  the  latter  as  the  nervous  system,  of 
organic  life. 

The  cerebrospinal  system  includes  the  brain  and  spinal 
cord,  the  nerves  associated  with  them,  and  their  ganglia, 
viz. : — The  ganglia  of  the  posterior  root  of  the  spinal 
nerves,  the  ganglion  of  the  fifth  nerve,  and  those  of  the 
glosso-pharyngeal  and  pneumogastric  nerves.  It  includes 
the  nervous  organs  in  and  through  which  are  performed 
the  several  functions  with  which  the  mind  is  more  imme- 
diately connected,  as  those  relating  to  common  sensation, 
volition,  and  the  special  senses,  as  well  as  those  concerned 
in  many  nervous  actions  with  which  the  mind  has  no 
connection. 

The  sym^pathetic  or  ganglionic  system  consists  of  a 
double  chain  of  ganglia  connected  by  nervous  cords,  which 


RUDIMENTARY  NERVOUS  SYSTEM. 


277 


extend  along  each  side  of  the  vertebral  column,  from  the 
cranium  to  the  pelvis,  and  from  which  nerves,  with  ganglia 
upon  them,  proceed  to  the  viscera  in  the  thoracic,  abdomi- 
nal, and  pelvic  cavities.  This  system  is  more  closely 
connected  with  the  process  of  organic  life  than  the  cerebro- 
spinal, but  is  less  immediately  connected  with  the  mind. 

In  the  lower  orders  of  the  animal  creation,  the  nervous 
system  is  quite  rudimentary.  In  the  ascending  series  of 
animal  life,  it  is  first  found  in  the  medusae  or  jelly-fishes. 
The  ganglionic  centres  are  situated  around  the  free 
margin  of  the  swimming  bell.  In  these  animals  also, 
is  seen  the  earliest  appearance  of  muscular  tissue  in 
the  animal  kingdom.  In  its  lowest  and  simplest  form  it  may 
consist  of  single  ganglionic  centres,  with  sensory  or  afferent, 
and  motor  or  efferent  nerves  (Fig  104;),  whose  function 
is  essentially  internuncial,  impressions  being  made  and 
responded  to  without  any  intervention  of  consciousness, 
the  movements  being  purely  exeito-motor.  A  simple  re- 
petition of  such  ganglionic  centres  may  exist  to  any  extent 
without  dissimilarity  of  function,  or  any  essential  departure 
from  the  mode  of  action  just  mentioned.  A  higher  form  of 
nervous  system  is  that  in  which  there  is  a  multiplication  of 
ganglionic  centres  to  correspond  with  the  diversity  of  func- 
tions, as  in  the  higher  articulata  and  mollusca,  in  which 
ganglionic  centres  are  set  apart  for  the  actions  of  deglutition 
and  respiration,  as  well  as  for  those  of  motion,  but  their 
modus  operandi  is  still  the  same — the  actions  being  all 
excito-motor.  In  all  but  the  very  lowest  invertebrata,  the 
nervous  system  includes,  in  addition  to  the  above,  certain 
ganglionic  centres  which  preside  over  the  organs  of  sight, 
smell,  hearing,  etc.  These  sensorial  ganglia  constitute  the 
*'  brain"  in  these  animals.  The  highest  degree  of  psychical 
perfection,  as  in  the  class  of  insects,  consists  in  the  ex- 
clusive development  of  the  instinctive  faculty,  or  of  simple 
automatic  powers,  by  virtue  of  which  each  individual  per- 
forms those  actions  to  which  it  is  prompted  by  impressions 


278 


THE  NERVOUS  SYSTEM. 


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made  upon  its  afferent  nerves,  without  any  self-control  or 
self-direction,  so  that  it  may  be  regarded  as  entirely  a 
creature  of  necessity. 

In  the  vertebrated  series,  on  the  other  hand,  the  highest 
degree  of  psj'chical  perfection,  as  shown  in  man,  consists  in 
the  highest  development  of  the  reason  t*ud  the  supreme 
domination  of  the  will,  to  which  all  the  automatic  actions — 
except  those  which  are  essential  to  the  organic  functions — 
are  subject,  so  that  each  individual  becomes  not  only  a 
thinking  and  reflecting,  but  also  a  self-moving  and  self- 
controlling  agent,  whose  actions  are  performed  with  a 
definite  purpose  in  view.  During  the  early  period  of  life, 
however,  the  mental  faculties  are  but  little  in  advance  of 
those  of  the  higher  invertebrata ;  for  example,  the  infant 
is  prompted  to  seize  the  nipple,  not  from  any  knowledge 
gained  by  experience,  that  by  so  doing  it  will  relieve  the 
feeling  of  hunger,  but  in  consequence  of  the  impulse  arising 
out  of  impressions  made  upon  the  afferent  nerves.  The 
super-addition  of  more  elevated  endowments  in  the  verte- 
brated series  is  coincident  with  the  addition  of  a  peculiar 
ganglionic  centre,  the  cerebrum,  to  the  sensori-motor  appa- 
ratus. 

The  superiority  of  the  mind  of  man  over  the  lower 
animals  consists  not  only  in  the  greater  variety  and  wider 
range  of  his  faculties;  but  also  in  that  dominant  power  of 
the  will  which  enables  him  to  utilize  them  with  the  highest 
effect.  When  the  thoughts  and  feelings  of  man  are  the 
mere  result  of  the  action  of  external  impressions  upon  a 
respondent  organism,  he  may  be  considered  irresponsible 
for  his  actions,  his  character  having  been  formed  for  him, 
and  not  hy  him.  But,  whenever  he  can  exert  a  volitional 
power  of  directing  his  thoughts  and  controlling  his  feelings, 
he  is  morally  and  intellectually  responsible  for  his  acts. 
Some  persons,  however,  in  consequence  of  the  weakness  of 
their  will,  are  so  much  accustomed  to  act  directly  upon  the 
prompting  of  any  transient  impulse,  that  they  can  scarcely 
be  said  to  be  voluntary  agents ;  and  others  allow  certain 


CRANIOSPINAL  AXIS. 


279 


dominant  ideas  or  habitual  feelings  to  gain  such  a  mastery 
over  them  as  to  usurp  for  the  time  the  power  of  the  will. 

The  fundamental  part  of  the  cerebro-spinal  system  is  the 
craniospinal  axis,  which  consists  of  the  spinal  cord, 
medulla  oblongata,  and  the  sensory  ganglia,  the  latter  con- 
sisting of  those  ganglia  lying  along  the  base  of  the  skull  in 
man,  and  in  which  the  nerves  of  the  special  senses  have 
their  origin,  viz.,  the  corpora  striata  and  quadrigemina,  the 
thalami  optici,  etc.  This  cranio-spinal  axis,  which  re- 
presents the  whole  nervous  system  of  the  invertebrata 
(except  the  rudimentary  sympathetic  they  posses.s),  exists 
without  any  super-addition  in  the  lowest  known  vertebrated 
animal,  as  in  the  case  of  the  little  fish  called  the  amphioxus. 
This  condition  may  even  be  found  in  the  human  species,  as 
in  the  case  of  acephalous  infants,  in  which  neither  the 
cerebrum  nor  cerebellum  is  present ;  such  have  existed  for 
several  days,  breathing,  sucking,  crying,  and  performing 
various  other  actions. 

In  man,  however,  and  in  all  the  higher  vertebrata,  large 
ganglia,  which  form  the  principal  mass  of  the  encephalon, 
are  found  superimposed  upon  and  embracing  the  sensory 
ganglia.  These  are  the  cerebrum  and  cerehdlwm ;  the 
former  is  the  seat  of  the  will,  and  presides  over,  controls, 
and  regulates  all  the  actions  and  movements  of  the  body, 
except  the  organic  functions  and  excito-niotor  actions  ;  the 
latter  is  concerned  in  the  regulation  and  co-ordination  of 
the  actions  of  the  spinal  cord.  The  action  of  the  cerebro- 
spinal system  may  be  elucidated  by  the  following  diagram 
— Caipenter. 


-i-The  Will 


Intellectual   operations 

+  . 
Emotions. 

+ 

-  Ideas. 

+ 
Sensations — 

I  Centre  of  Bensori-uiutor  reflexion. 


1.. 


i-  Cerebrum. 

Centre  of  emotional  and    ideo-tnotor  re- 
flexion. 


-+■  Sensory  jjanglia- 


Impressions +-  Spinal  Cord 


Motor  Impulse. 


Centre  of  excito-niotor  reflexion. 


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280 


THE  NERVOUS  SYSTEM. 


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In  consequence  of  the  peculiar  arrangement  of  the 
nervous  apparatus,  excitor  impressions  travel  in  the  upward 
direction  ;  so  in  the  left-hand  corner  of  the  diagram  the 
iinpTessions  are  represented  as  passing  upwards.  If  they 
meet  with  no  interruption,  they  travel  upwards  through 
the  spinal  cord  until  they  reach  the  sensorium  or  sensory 
ganglia,  where  they  make  an  impression  on  the  conscious- 
ness of  the  individual,  giving  lise  to  sensations.  These, 
passing  from  the  sensoiy  ganglia  io  the  cerebrum,  form 
idea8>  If  these  ideas  are  associated  with  feelings  of  pain  o  • 
pleasure,  they  give  rise  to  emotions ;  and  either  as  simple 
or  emotional  ideas,  they  become  the  subject  of  intellectual 
operations  whose  final  issue  culminates  in  an  act  of  the 
luill,  which  may  be  e.-erted  in  producing  or  checking  a 
muscular  movement,  or  in  controlling  or  directing  the 
current  of  thought. 

If  this  ordinary  upward  course  be  interrupted,  or  if  the 
action  be  excito-motor, the  impressions  'villexert  their  power 
in  the  transverse  direction,  and  a  reflex  action  will  be  the 
result;  for  example,  if  the  interruption  be  produced  by 
division  or  injury  of  the  spinal  co/d,  below  the  sensory 
ganglia,  reflex  movements  being  produced  without  sensation 
will  be  purely  excito-motor.  So,  again,  if  the  connection 
between  the  sensory  ganglia  and  the  cerebrum  be  severed, 
or  if  the  function  of  the  cerebrum  be  in  abeyance,  they  n)ay 
react  on  the  motor  apparatus  by  the  reflex  power  of  the 
sensory  ganglia  themselves  ;  such  actions,  being  dependent 
on  the  promptings  of  sensation,  are  sensori-motor. 

The  alferent  and  efferent  nerves,  and  their  connection 
with  the  spinal  cord,  constitute  an  excito-motor  nerve  arc, 
and  the  spinal  cord  consists  of  a  longitudinal  series  of  excito- 
motor  arcs,  since  an  impression  may  be  made  through  the 
afterent  nerve  which  produces  action  of  the  muscles  supplied 
by  the  efl'erent  nerve,  the  whole  being  consumed  without  leav- 
ing behind  any  impression  on  the  nervous  centre.  The  nerve 
arc  may  be  connected  to  a  ganglion  by  means  of  a  band  or 


STRUCTURE  OF  THE  NERVOUS  SYSTEM.      281 


commissure,  tlirough  which  a  por^on  of  the  nervous  in- 
fluence passes  to  be  stored  up.  This  is  called  a  registering 
ganglion,  as,  for  example,  the  corpus  striatum,  thalamus 
opticus,  etc.,  and  these,  in  their  turn,  are  connected  to  the 
cerebrum,  this  connection  constituting  what  is  called  the 
influential  arc.  The  registering  ganglia  are  regarded  as 
the  sensorium,  and  correspond  with  the  sensory  ganglia. 
Their  function  appears  to  be  to  receive  and  retain  impres- 
sions of  ideas,  events  or  occurrences,  the  time,  place,  and 
order  in  which  they  occurred,  and  other  circumstances 
which  are  usually  ascribed  to  the  faculty  of  memory. 

Structure  of  the  Nervous  System. — The  organs  of 
the  nervous  system  are  composed  essentially  of  two  dirlerent 
elements,  nerve  fl^hres  and  nerve  cells.  The  former,  on 
account  of  their  color,  are  often  called  the  white  or 
medullary  substance ;  the  latter,  the  gray  or  cineritious 
substance. 

Nerve  Fibres. — There  are  two  different  kinds  of 
nerve  fibres,  the  niedullated  and  the  non-medullated. 
They  are  intermingled  in  most  nerves,  the  former  being 
more  numerous  in  the  cerebro-spinal  .system  ;  the  latter  pre- 
dominating in  the  sj^mpathetic. 

The  medullated  nerve  fibres  consist  of  tubules  of  simple 
homogeneous  membrane,  the  neurilemma,  similar  to  the  sar- 
colemma  of  striated  muscular  tissue,  within  which  is  con- 
tained the  proper  nerve  substance,  consisting  of  two  differ- 
ent materials.  The  central  part  consists  of  a  greyish  ma- 
terial called  the  axis  cylinder ;  the  outer  portion  which 
surrounds  the  axis  cylinder  is  usually  opaque,  and  dimly 
granular,  and  is  called  the  white  substance  of  Schwann.  It 
is  the  predominance  of  this  substance  which  gives  the 
cerebro-spinal  nerves  their  white  appearance.  The  axis 
cylinder  consists  of  a  Krge  number  of  primitive  fibrillae,  and 
is  the  conductor  of  nerve  force.  It  is  the  es.sential  element 
of  the  nerve  tube,  and  may  be  compared  to  the  "  core  "  of 
the  submarine  cable ;  the  white  substance   of  Schwann  to 


282 


THE  NERVOUS  SYSTEM. 


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the  insulating  layer  of  gutta-percha,  and  the  tubular  mem- 
brane or  sheath,  to  the  outer  coating  of  rope,  merely  afford- 
ing mechanical  protection,  and  serving  to  isolate  it  from  the 
neighboring  fibres.  The  axis  cylinder  is  readily  stained 
with  carmine,  the  white  substance  of  Schwann  remaining 
unaffected  ;  while  chromic  acid  renders  the  latter  brown  and 

opaque,  but  has  no  action  on  the 
former.  In  the  recent  state  the 
nerve  tubes  are  cylindrical,  and 
contain  a  transparent  and  apparent- 
ly homogeneous  material,  but  after 
death  they  present  a  dark  double . 
contour,  the  outer  line  being  formed 
by  the  tubular  membrane  or  sheath, 
the  inner  by  the  white  substance  of 
Schwann.  At  the  same  time  the 
white  substance  and  axis  cylinder, 
which  now  appear  granular,  collect 
into   little   masses    whLh    distend 

Medullated  nerve  fibres  ;  a,  broad    v.-^.^finnci  nf  fVip  fnhnlnr   mprnVirnnA 
fibre;  b,  torn  fibre  with  axis  cylin-    pOrUlOnS  01    tne  tUDUiai    memoraUC, 

w1dthrd"e!'fln^fib"es'°''"''''"'"  whilc  the  intermediate  spaces  col- 
lapse, giving  the  fibres  a  varicose  or  beaded  appearance.  The 
contents  of  the  nerve  tubes  are  very  soft,  and  readily  pass 
from  one  part  of  the  canal  to  another,  or  escape  from  the 
ends  of  the  tube  on  pressure.  The  nerves  vary  in  size  from 
aTs^oo  ^^  50*00  of  an  Inch  (12.  uO  8.  mmm)  in  diameter  in  the 
trunk  and  branches  of  nerves,  but  are  smaller  in  the  gray 
matter  of  the  brain  and  spinal  cord,  in  which  they  are  sel- 
dom more  than  Tff(Wrf  to  ttooo  of  an  inch  (2.5  to  2  mmm). 
.  Non- medullated  nerve  fibres  constitute  the  olfactory 
nerves,  the  principal  part  of  the  trunk  and  branches  of  the 
sympathetic,  and  are  mingled  in  various  proportions  in  the 
cerebro-spinal  nerves.  They  differ  from  the  medullated  nerves 
in  their  fineness,  being  only  one-half  or  one-third  as  large 
(TTFVoto-g^uVxraninchjG  to4  mmm);  in  the  absence  of  the  double 


NERVE  CELLS. 


28Ji 


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ictory 
)f  the 
In  the 
lervcs 

large 
llouble 


Fife'.  o<i.  contour;  in  their  apparently  uniform  struc- 

turc,  and  yellowish  gray  color.  These  fibres 
consist  of  the  sheatli  aiul  the  sub.stance 
which  corresponds  with  the  axis  cylinder 
of  the  mcdullated  nerves,  and  difi'er  from 
them  in  not  ])ossessing  the  white  substance 
of  Schwann.  In  the  liner  divisions  of 
nerve  fibres  the  axis  cylinder  is  frequently 
found  without  any  covering  whatever. 

Nerve  Cells. — Nerve   cells  or  ganglion 

corpuscles   are   found   in    the   brain,  spinal 

cord,  and  the  various  ganglia  mingled  with 

,  ,.  nerve  fibres,  beintif  imbedded  in  a  tine  stroma 

Sympathetic  -.lerve  '  c^ 

""iiich  a;e'scen"two  ^^  rotiform  tissuc  Called  the  neuroglia,  and 
llbrcs.'^a!'''^'""^''  "^"''^  give  to  thesp  structures  a  peculiar  reddish- 
gray  color.  They  pre-  ^'"  "'• 
sent  different  shapes, 
some  being  spheroi- 
dal or  apolar,  others 
caudate  or  unipo- 
lar, and  others  bi- 
polar, multipolar  or 
stellate,  some  of  the 
processes  being  con- 
tinuous with  a  nerve 
fibre.  They  vary  in 
size  from  ^U  to  tttUo 
of  an  inch  (83  to  2,.') 
mmm)  in  diameter. 
Each  cell  contains  a 
vesicular  nucleus,  and 
nucleolus,  the  latter 
being  generally  clear 

,,.■,,  '     1        1  Ncrvo  cells  ;  a,  apohu- ;  It,  miipol.ir  ;  (',  <•,  niultipDlar 

and  bright;    and   the  ceiis. 


contents 

color. 

i6 


are    finely    granular,   and    of    a 


reddish    gray 


ii84 


THE  NERVOUS  SYSTEM. 


c 
c 

mt 
fl 
I. 

^ 

•V 

I' 

r 

Mi 
^. 

r 


A  nerve  ganjjlion,   showing  the  iirraiige- 
mciit  of  nerve  cells  and  nerve  fibres. 


Ganglia. — These  may  be  regarded  as  separate  and  inde- 
pendent nervous  centres,  of  smaller  size  than  the  brain,  and 
less  complex.  They  are  found  on  the  posterior  roots  of  the 
spinal  nerves  ;  on  the  posterior  root  of  the  fifth  nerve ;  on 
the  facial,  olfactory,  glosso-pharyngeal  and  pneumogastric 
nerves ;  along  the  base  of  the  brain, as  the  corpora  striata, 
^'^'•^^*  corpora     quadrigemina    and 

thai  ami  optici ;  on  each  side 
of  the  vertebral  column  form- 
ing the  trunk  of  the  sympa- 
thetic, and  on  some  of  its 
branches  of  distribution.  In 
structure  they  are  similar  to 
other  nervous  centres,  beins: 
composed  of  a  collection  of 
nerve  cells,  and  medulla  ted  and  non-medallated  nerve  fibres. 
They  are  of  a  reddish -gray  color. 

Chemical  Composition  of  Nehve  Tissue. — Nervous 
matter  of  the  brain  is  a  soft,  unctuous  substance,  easily 
lacerated,  and  contains  about  75  per  cent,  of  water,  15 
parts  of  fatty  matter,  7.5  of  albuminous  compounds,  1.5  of 
salts,  and  1  of  extractive  matter.  The  fatty  matter  is  more 
abundant  in  the  white  than  in  the  grey  substance.  Among 
the  albuminous  substances  are  to  be  found,  cerebrin,  lecithin 
myosin,  creatin,  xanthin  etc.  From  the  fatty  matters  may 
be  obtained  carbonic  ac'd,  cholesterine,  phosphoric  and  oleo- 
phosphoric  acids,  traces  of  oleine,  margarine,  and  fatty  acids. 
The  quantity  of  phosphorus  is  wqyj  large.  The  spinal  cord 
is  said  to  contain  a  larger  proportion  of  fat  than  the  brain. 

Corpora   Amylacea. — These   are  small, ^'«-  ^^• 

rounded  bodies,  identical  with  starch  granu- 
les, from  tVtjw  to  T-rV  5  of  an  inch  (5.5  to  22.5 
mmm)  in  diameter,  which  are  found  in  the 
fornix,  septum  lucidum  and  lateral  ven- 
tricles of  the  brain.  They  are  transparent, 
soft,  irregularly  rounded  and  present  a  star-     corpora  amyiacea. 


DISTRIBUTION  OF  NERVE  FIBRES. 


285 


shaped  pore  with  a  faint  laminar  arrangement.  They  give 
a  blue  color  when  treated  with  iodine  and  sulphuric  acid. 
The  physiological  relations  of  these  bodies  are  not  known. 

Distribution  of  Nerve  Fibres. — Nerve  fibres  consist 
of  round  or  flattened  cords,  communicating  on  the 
one  hand  with  the  nervous  centres,  and  on  the  other 
distributed  to  the  various  textures  of  the  body,  forming  the 
medium  of  communication  between  the  two.  They  are 
divided  into  two  great  classes,  the  cerebrospinal,  or  nerves 
of  animal  life,  distributed  to  the  organs  of  the  senses,  the 
skin,  and  the  muscles ;  and  the  si/mpathctio  or  nerves  of  or- 
ganic life,  distributed  chiefly  to  the  viscera,  and  blood- 
vessels. 

The  cerehro-spinal  nerves  con .^ist  of  a  number  of  primi!;ive 
nerve  fibres,  enclosed  in  a  simple  membranous  sheath.  These 
are  called  funiculi,  and  if  the  nerve  is  of  small  size  it  may 
consist  of  only  one  funiculus ;  but  if  large,  there  may  be 
several  connected  together  by  a  common  sheath  formed  of 
areolar  tissue.  Every  nerve  fibre  pursues  a>i  uninterrupted 
course  from  its  origin  at  a  nervous  centre,  to  its  destination, 
whether  this  be  the  i)eriphery  of  the  body,  in  another 
nervous  centre,  or  the  same  from  which  it  issued.  They 
anastomose  or  communicate  with  each  other  iu  their  course, 
sometimes  joining  at  acute  angles  with  others  proceeding 
in  the  same  direction  ;  but  they  never  coalesce,  or  unite  with 
the  substance  of  any  other  fibre  ;  for  although  they  cross  and 
mingle  with  each  other,  yet  each  separate  nerve  fibre  re- 
tains its  identity  throughout.  The  nerves,  iu  certain  parts 
of  their  course,  form  plexuses  in  which  the3'  anastomose  with 
each  other,  as  in  +,he  cervical,  brachial,  lumbar,  and  sacral 
plexuses.  In  the  formation  of  a  plexus,  the  component  nerves 
divide,  then  unite,  and  again  sub-divide,  and  in  this  way 
the  fasciculi  become  intricately  interlaced.  The  object  of  such 
interchange  of  fibres  is  to  give  each  nerve  a  wider  connection 
with  the  spinal  cord,  so  that  the  [)arts  su[)plied  may  have 


286 


THE  NERVOUS  SYSTEM, 


c 
c 

MM 

L 

I- 

m. 

«). 
I 


B 

tS'l 


B 

tS'l 

«1 


»«. 
rsi 
tiii.i . 


wider   relations  witli   the   nervous  centres,  and   also   that 
groups  of  muscles  may  be  associated  for  combined  action. 

OiiKHN  AND  Termination  of  Nerves. — The  point  of 
connection  of  a  nerve  with  the  brain,  spinal  cord,  or  r^anglion 
is    called,  for  convenience   of  description,  its   origin,  root 
or  central  termination ;  the  point  of  distribution  its  'peri- 
pheral termination ,  or  peripherij. 

With  reference  to  their  origin,  some  of  them  originate  in 
nerve  corpuscles,  or  their  prolongations,  others  probably  form 
simple  loops.  As  the  nerve  fibre  approaches  the  nerve  cor- 
puscle or  its  prolongation,  the  white  substance  of  Schwann 
gradually  disappeais,  the  tubular  membrane  or  sheath  blends 
with  the  nerve  corpuscle,  and  the  axis  cylinder  becomes  con- 
tinuous with  the  contents  of  the  cell.  More^fil>res  have  been 
counted  leavingthan  entering  a  ganglion,  from  which  it  may 
be  inferred  that  some  of  them  arise  from  the  corpuscles.  It 
has  not  yet  been  determined  whether  this  relation  of  nerve 
fibres  to  nerve  cor})usoles  is  common  to  all  kinds  of  nerve 
fibres.  Some  are  of  oi)inion  that  sensitive  fibres  alone  are 
])i'ought  into  this  intimate  relation  with  nerve  corpuscles. 
1 1  does  not  appear,  however,  to  belong  exclusively  to  either 
the  cerebro-spinal  or  S3nn])athctic  nerves. 

The  peripheral  termination  is  also  exceedingly  difficult 
to  determine,  but  examples  of /li'e  different  modes  have  been 
observed. 

1st.  In  loops  or  plexuses.  In  this  mode  of  termination, 
each  fibre,  after  issuing  from  a  branch  in  a  terminal  plexus, 
runs  over  or  through  the  substance  of  the  tissue ;  it  then 
turns  back  and  joins  the  same,  or  avi  adjaceni  branch,  and 
pursues  its  way  back  to  the  nervous  centre.  This  mode  has 
been  found  in  mucous  and  serous  membranes,  in  the  anterior 
epithelium  of  the  cornea  and  in  muscular  ti.ssue. 

2nd.  In  terminal  bulbs,  csdled  tactile  corpuscles  of  Meisii- 
ner  and  Wagner,  (Fig.  100  A) ;  end-bulbs  of  Krause,  (Fig. 
100  B) ;  and  Pacinian  bodies,  or  corpuscles  of  Vater  (Fig. 
10 1.)     Tlio  tactile  corpuscles  are  oval  shaped  bodies,  formed 


-2T5PK-— 


TERMINATION  OF  NERVES. 


287 


•of  delicate  connective  tissue, 
ju'ound  winch  the  nerve 
passes  in  a  spiral  manner. 
They  are  found  in  the  ]mp- 
illa'  of  tln^  skin,  especially  in 
the  palms  of  the  hands  and 
the  soles  of  the  feet.  Thcnr 
length  is  about  ^i,,  and  their 
thickness  ^i,,  of  an  inch  (100 
to  50  mmm).  The  end-hulh.9 
of  Krause  resemble  the  tac- 
tile corpuscles  in  api)earanco, 

but  are  .-jmaller  and  more  a.  cutmeonsiapmaof  tllollillul;ra,)t•orti- 
,      .  ,  cal  layer  williceils and  L'liiHtictlliros;  (fc)  tactile 

Simple   in    structure.  Ihey    corptiacle  ;  (c,  </)  nerve  nbres.      fl.  Knd  bulb.s 

of  Krause;  (a)  coverinff  of  nerve,  bulb;  (d) 
interior  of  bulb  ;  (c)  nerve  fibre. 


form   a   round  or 

Fijr.  101. 


oval  en- 
largement homogeneous  in  structure, 
at  the  extremity  of  the  nerve,  and 
are  found  in  the  conjunctiva,  floor 
of  the  mouth,  the  tongue,  the  glans 
penis,  and  the  clitoris. 

The  Pacinian  corpuscles  are  small 
oval  bodies,  situated  on  some  of  the 
the  cerebro-spinal  and  sympathetic 
nerves,  especially  the  cutaneous 
nerves  of  the  hands  and  feet.  They 
are  named  after  their  discoverer 
Pacini.  They  are  most  distinctly 
seen  in  the  mesentery  of  the  cat. 
Each  corpuscle  is  attached  to  the 
nerve  on  which  it  is  situated  by  a 
rnuscie.  1,  base;  uarrow  pediclc,  and  is  formed  of  con- 

^  -.  _    .     ,   _,   _ubstance  tof  the  ' 

•orpuscie.  in  layers ;  4, 4,  nerve  ccntric  lavci's  of  fine  membrane,  with 

jienetratinjf    the    corpuscle;   5,  '' 

-avity  of  the  corpuscle;  6,  nerve;  intervening  spaccs  filled  with  fluid. 

7,  nerve,  which  has  lost  its  nie-  '^     ^ 

aullary  substance   and    sheath;    A  siuglc    ncrVC    fibre    paSSCS    thrOUgh 
>,  tcniiination  of  the  nerve ;  9.  o  ^  O 

vvSrthe\me*^'\s%pef^^       ^^®  peiUclc,  and  after  traversing  the 


A  Pacinian  cor 
apex ;   :i,   3,   sub 


288 


THE  NERVOUS  SYSTEM. 


c 
c 

t 
I. 


an 


tlU:l. 


Fig.  102. 


several  layers  of  membrane,  it  terminates  in  the  centra? 
cavity  in  a  bulbous  enlargement,  or  a  bifurcation  (Fig.  101/ 
The  function  of  these  bodies  is  not  known;  they  are  pro- 
bably reservoirs  for  nerve  force. 

3rd.  In  motorial  md-plates,  as  described  by  Rouget  and 
others.  This  is  the  mode  of  termination  in  striated  muscular 
tissue.  As  the  nerve  fibre  approaches  the  muscular  fibre  it 
expands,  the  sheath  blends  with  the  sarcolemma,  the  white 
substance  of  Schwann  terminates  abruptly,  and  the  axis 
cylinder  spreads  out  beneath  the  sarcolemma  on  the  sur- 
face of  the  fibrilho,  forming  an  oval  plate  from  -sU  to  Toio 
of  an  inch  (50  to  25  mmm)  in  diameter  (Fig's  38  and  102) 

4th.  Some  nerves  appear  to  termi- 
nate in  cells,  or  nerve  corpuscles,  aw 
those  of  the  eye,  interal  car  and  other 
parts. 

5th.  In  free  ends  as  from  the  fine 
plexuses  in  non-striated  muscular 
tissue,  and  in  the  cornea. 

Some  nerve  fibres  appear  tohaveno 
peripheral  termination.     It  has  been 

Termination  of  a  nerve  fibre    sllOWn    by    Gcrbcr   that   nCrVC    fibres 
bv  anii)ti)rial  eiul-plate  in  anuis-  •  11      r  1  i  1      •      • 

ciiiar  fibre  (Longet.)  occasioually  tomi  loops  by  their  junc- 

tion with  a  neighboring  fibre  in  the  same  fasciculus,  and 
return  to  the  nervous  centre  without  having  any  peripheral 
termination.        He   considers  *''^'-  ^"•'• 

these  to  be  sentient  nerves,  for 
the  suppl}^  of  the  nerve  itself, 
the  nervi  nervorum,  upon 
which  the  sensibility  of  the 
nerve  depends.  This  is  some- 
v^hat  similar  to  those  nerve 
fibres  met  with  at  the  posterior 
part  of  the  optic  commissure, 
where  a  set  of  fibres  pass  from  The  optic  commissure, 

one  optic  tract  across  the  commissure  to  the  tract  on  the 


FUNCTION  OF  NERVE  FIISKES. 


28J> 


opposite  side,  without  having  any  connection  with  the  optic 
nerves — the  inter-cerebral  fibres;  other  i  appear  to  have  no 
central  connection  with  the  cerebro-spinal  centre,  as  those 
forming  the  anterior  fibres  of  the  0])tic  commissure — the 
inter-retinal  fibres.  These  commence  in  the  retina  on  one 
side,  pass  along  the  optic  nerve,  and  across  the  commissure  to 
the  retina  of  the  opposite  side. 

Medullated  nerve-fibres  lose  the  white  substance  of 
Schwann,  before  their  final  distribution,  and  bear  a  close  le- 
semblance  to  the  non-modullated  fibres. 

The  sympathetic  nerves  consist  of  medullated  and  non- 
medullated  fibres,  intermingled  in  various  proportions  in 
different  nerves,  and  are  enclosed  in  a  sheath  of  areolar 
tissue.  The  mode  of  distribution  of  these  nerves  is  essen- 
tially the  same  as  that  of  the  cerebro-spinal.  The  most 
striking  peculiarity  is  the  frequent  formation  of  ganglia  in 
the  coui'se  of  the  trunk  and  their  branches.  They  are 
chiefly  distributed  to  the  head  and  trunk,  being  very  limited 
in  their  connection  with  the  extremities. 

Function  of  NerveFibres. — The  functions  of  nerve  fibres 
and  neive  centres  are  determined  by  comparing  their  a7ia- 
tomy  in  man  with  that  of  the  lower  animals;  by  experiments 
on  recently-killed  or  living  animals,  and  by  clinical  obser- 
vation. 

The  office  of  the  nerves  is  to  convey  or  conduct  nervous 
impressions.  The  function  is  of  a  two-fold  kind — -first,  they 
serve  to  convey  to  the  nervous  centres  the  impressions  made 
upon  their  peripheral  extremities,  or  on  parts  of  their 
course  ;  and,  secondly,  they  serve  to  transmit  impressions 
from  the  brain,  and  other  nervous  centres,  to  the  parts  to 
which  they  are  distributed.  These  impressions  are  of  two 
kinds,  viz.,  those  that  excite  muscular  contraction,  and 
those  which  influence  the  processes  of  secretion,  growth,  ttc. 

Those  ner\  ts  that  convey  impressions  from  the  periphery 
to  the  centre,  are  called  sensitive,  centripetal  or  afferent 
nerves,  or  nerves  of  sensation;  and  those  which  transmit  im- 


iOO 


THE  NERVOUS  SYSTEM. 


c 
c 

L 

I 


vet' 

•t5  ■ 


Fi(f    104. 


pulses  to  the  muscles,  are  called  inoto7\  centnfugal  or  effer- 
ent nerves,  or  uervea  of  luotion.  This  peculiarity  cannot 
be  account*  (1  for  from  any  special  variety  of  structure  which 

the  nerves  possess,  or  the  tis- 
sues to  which  they  are  distri- 
buted. The  two  kinds  of 
nerves  lie  side  by  side  in  the 
same  sheath.  Those  which 
surface  havc  no  peripheral  termination 


1. 


Diaffraiu    of  reflex    action ; 
(ei)itliuliuiii) ;  2,  iniisole ;  A,  iiorve  of  NcriKa-  ii     i         '     j  i        l         _ 

tion;  B.  ocntrki  ncrvc.\eii;  c,  ne.veof  are     Called     mfercentrctl,     as 

motion :  A,  U,  C,  form  the  )ic»TC  ncr  wliich    ,.  i     ii        i        i  i      /?  xi 

presides  over  reflex  action.  thOSC  at    the    baCK    part  01    tllO 

optic  commissure.  The  nervous  force  (vis  nervosa)  by  which 
secretion,  nutrition,  etc.,  are  influenced,  seems  to  be  conveyed 
aUmg  both  sensitive  and  motor  nerves. 

Nerve  fibres  require  to  be  stimulated,  in  order  to 
manifest  their  peculiar  endowments,  since  they  do  not  pos- 
sess tlie  power  of  generating  force  in  themselves,  or  of  ori- 
ginating impulses  to  action.  The  property  of  conducting 
impressions  is  called  excitability ;  but  this  is  never  mani- 
fested until  some  stimulus  is  applied.  The  stimuli  by 
which  the  action  of  nerves  is  ordinarily  provoked,  are  of 
two  kinds,  mental  and  phymcal ;  the  former  relates  to  the 
will,  the  latter  to  the  influence  of  external  objects,  and 
chemical,  mechanical  and  electric  actions  or  irritations. 
These  stimuli  when  ^applied  to  parts  endowed  with  senia- 
tion,  or  to  .'sensitive  nerves,  produce  sensations,  and  when 
applied  to  the  nerves  of  muscles  produce  contractions. 
Nerves,  though  divided,  when  irritated  or  stimulated  have, 
by  virtue  of  their  excitability,  the  power  of  exciting  con- 
tractions in  the  muscles  to  which  they  are  distributed ;  but 
when  the  ct)ntinuity  of  the  nervous  matter  is  broken,  or 
the  fibre  bruised,  or  seriously  injured,  the  property  of  propa- 
gating nervous  force  is  destroyed.  Nervous  action  is  also 
excited  by  temperature ;  for  example,  any  very  hot  substance 
applied  to  the  body  produces  muscular  contraction,  and  a 
sensation  of  pain  is  transmitted  to  the  nervous  centre ;  the 


LA  IVS  OF  ACT/ON  IN  NERVE  FIBRES. 


291 


;on- 

but 

or 


the 


application  of  a  very  cold  substance  has  a  somewhat  similar 
effect.  Chemical  stimuli  excite  the  action  of  both  sensitive 
and  motor  nerves,  when  their  effect  is  not  so  strong  as  to 
destroy  the  structure  of  the  nerve  to  which  they  are  applied. 
A  similar  manifestation  of  nervous  power  is  produced  by 
electricity.  Nerve  force  travels  along  the  fibres  with  im- 
mense rapidity  ;  its  velocity  has  beon  ascertained  by  Helra- 
holtz  and  others  at  111  feet  per  second  in  motor,  and  140  in 
sensory  nerves. 

Lav,^s  of  Action  in  Neuvk  Fiuuks. — All  nerve  fibres 
are  mere  conductors  of  impressions.  An  impression  made 
on  any  fibre  is  transmitted  along  it  without  interruption, 
and  without  being  imparted  to  any  of  the  fibres  lying  near 
it.  This  is  probably  due  to  the  fact,  that  the  contents 
of  each  fibre  arc  isolated  from  those  of  adjacent  fibres,  by  the 
membrane  or  sheath  in  which  it  is  enclosed.  It  is  also  sup- 
posed that  the  white  substance  of  Schwann  acts  as  an  in- 
sulatoi".  No  nerve  fibre  can  convey  more  than  one  kind  of 
impression  ;  for  example,  the  motor  nerve  conveys  only 
motor  impulse  ;  the  sensitive  nerve  transmits  only  sensation 
when  propagated  to  the  brain,  and  the  nerves  of  special 
sense,  as  the  optic  and  auditory,  convey  only  sensations  of 
light  and  sound.  Nerves  of  sensation  are  able  to  convey 
impressions  only  from  the  parts  to  which  they  are  distri- 
buted, towards  the  nervous  centre  with  which  they  com- 
municate ;  for  example,  whon  a  sensitive  nerve  is  divided, 
and  irritation  is  applied  to  that  portion  still  connected  with 
the  nervous  centre,  sensation  is  perceived,  or  a  reflex  action 
ensues ;  but  w^hen  the  distal  portion  is  irritated  no  effect  is 
produced.  When  the  trunk  of  a  nerve  is  irritated,  the  sen- 
sation is  felt  in  all  the  parts  which  receive  branches  from 
it ;  for  example,  if  the  ulnar  nerve  be  compressed  behind  the 
internal  condyle  of  the  humerus,  a  peculiar  tingling  sensa- 
tion is  felt  in  the  little  finger,  and  in  the  ulnar  half  of  the 
ring  finger.  Even  when  part  of  a  limb  has  been  amputated, 
any  pressure  or  irritation  to  the  remaining  portions  of  the 


292 


THE  NERVOUS  SYSTEM. 


c 
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nerves  which  ramified  in  it,  gives  rise  to  sensations  whicli 
the  mind  refers  to  the  lost  part,  as  well  as  to  the  stump,  and 
tiuglings  and  pains  are  complained  of  in  the  lost  finger,  toe, 
hand  or  foot,  as  the  case  may  He.  Again,  when  the  relative 
position  of  the  peripheral  extremities  of  sensitive  nerves  is 
changed  artificially,  as  in  the  restoration  of  the  nose  from 
the  integument  of  the.  forehead,  the  sensation  produced  when 
the  new  nose  thus  formed,  while  connected  by  its  isthmus, 
is  touched,  is  referred  to  the  forehead.  This  j)eculiarity  may 
be  exemplified  by  the  following  experiment : — Cross  the 
middle  fingar  of  the  hand  behind  the  index  finger  so  that 
the  extremity  is  on  the  radial  side  of  the  latter,  then  roll  the 
two  fingers  over  a  pea  or  marble,  and  a  sensation  will  be 
produced  which  leads  the  mind  to  suppose  the  existence  of 
two  distinct  bodies.  This  is  owing  to  the  impression  being 
made  at  the  same  time  on  the  sides  o:^  the  fingers  most  re- 
moved from  each  other  in  the  natura  .position.  Generally, 
however,  the  mind  discerns  the  exact  part  of  a  nerve  fibre 
that  is  irritated,  and  even  when,  as  is  the  case  in  the  retina, 
two  or  more  impressions  are  made  at  the  same  instant  on 
dift'erent  parts  of  the  same  fibre,  the  mind  can  discriminate 
and  perceive  each,  and  compare  the  one  with  the  other. 

Several  of  the  laws  of  action  in  motor  nerves  are  similar 
to  the  foregoing.  For  example,  motor  influence  is  trans- 
mitted only  in  the  direction  of  the  fibi.'s  going  to  the 
muscles,  and  ir]-itation  of  a  motor  nerve  excites  contraction 
in  all  the  muscles  supplied  by  the  branches  given  off"  below 
the  point  of  irritation  ;  but  those  supplied  by  branches  given 
off'  above  this  point  are  never  directly  affected.  Again, 
since  motor  nerves  are  isolated  as  completely  as  sensitive, 
the  irritation  of  a  part  of  the  fibres  of  a  motor  nerve  does 
not  affect  the  motor  power  of  the  whole  trunk,  but  only 
that  of  the  portion  to  which  the  stimulus  is  applied. 

Development  of  Nerve  Tissue. — Keive  fibres  appear 
to  be  formed  in  the  same  manner  as  muscles.  The  primitive 
cells  are  imbedded  in  protoplasm  or  intercellular  substance 


DEVELOPMENT  OF  NERVE  TISSUE. 


29:1 


[ear 
live 
bee 


which  is  arranged  in  the  shape  and  form  of  the  developinir 
nerve  fibre.  The  cells  elongate,  the  nuclei  increase  in 
number,  and  the  protoplasm  and  cell  contents  become  trans- 
formed into  the  different  parts  of  the  nerve  fibre —  viz,  the 
sheath,  white  substance  of  Schwann,  and  axis  cylinder  or 
"  band  of  Remak."  In  the  nerve  centres  the  cells  remain  in 
their  primitive  state,  the  only  change  being  that  they  in- 
crease in  size,  and  dcvelope  in  their  interior  some  pigmentary 
granules. 

In  the  process  of  regeneration,  after  incision  or  injury,, 
the  extremities  of  the  nerves  are  united  at  first  by  fibrous 
tissue,  which  after  a  time  is  replaced  by  nerve  tissue,  if  the 
cut  extremities  are  not  too  far  removeil.  Perfect  restoration 
of  the  action  of  the  nerve,  however,  does  not  generally  take 
place,  owing  probably  to  the  want  of  exact  coaptation 
between  the  cerebral  and  peripheral  i)ortions  of  the  same 
fasciculi ;  for  example,  the  cerebral  portion  of  a  motor  fila- 
ment may  unite  with  the  peripheral  portion  of  a  sensitive 

one,  and  the  action  of  each  will  be  partially  neutralized. 

Vascular  Supply. — The  blood-vessels  supplying  a  nerve 
terminate  in  a  minute  capillary  plexus,  disposed  similarlj'' 
to  those  of  muscles,  running  parallel  to  the  nerve  fibres. 
Thoy  are  connected  together  by  short  transverse  branches, 
forming  narrow  oblong  meshes. 

Function  of  the  Nervous  Centrb:s. — The  nervous  cen- 
tres embrace  all  those  parts  of  the  nervous  system  which 
contain  nerve  corpuscles,  as  the  brain,  spinal  cord,  and  the 
ganglia  of  the  cerebro-spinal  and  sympathetic  system.  Their 
function  is  that  of  variously  disposing  and  transferring  the 
impressions  received  through  their  several  sensitive  nerves. 
Nerve  fibres,  as  already  stated,  are  simply  conductors  of 
nervovs  influence.  Nervous  centres  are  not  only  conduc- 
tors, but  also  communicators  and  reflectors  of  nervous  im- 
pressions. The  brain  conducts,  communicates,  rejiects,  and 
perceives  or  takes  cognizance  of  impressions. 


294 


THE  NERVOUS  SYSTEM. 


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Conduction. — When  an  impression  is  produced  on  the 
periphery  of  a  nerve,  as,  e.  g.,  in  the  mucous  membrane  of 
the  intestines  by  the  presence  of  a  portion  of  food,  it  is 
conducted  to  the  adjacent  ganglia  of  the  sympathetic,  from 
which  a  motor  impulse  returns  to  the  intestines  and  pro- 
duces a  movement  of  the  muscular  coat.  If,  however,  any 
irritant  substance,  as  a  drastic  cathartic,  be  mixed  with  the 
food,  a  stronger  impression  is  produced,  and  this  is  con- 
ducted through  the  nearest  ganglia  to  others  more  remote, 
and  from  all  these,  motor  impulses  proceed  which  excite  a 
more  forcible  and  widely  extended  action  of  the  small  in- 
testine ;  or  the  impression  may  be  conducted  through  the 
ganglia  of  the  spinal  cord,  from  which  motor  impulses  may 
proceed  to  the  abdominal  and  other  muscles,  producing 
cramp.  Besides,  the  same  morbid  impression  may  be  con- 
ducted through  the  spinal  cord  to  the  cerebrum,  where  the 
mind  can  perceive  and  take  cognizance  of  it. 

Communication. — Impressions  made  on  the  nervous  cen- 
tres may  be  cortimunicated  from  the  fibres  that  brought 
them  to  others,  and  in  this  communication  they  may  be 
either  transferred  or  diffused.  The  transference  of  im- 
pressions may  be  seen  in  disease  of  the  hip  joint.  The  im- 
pression made  by  the  disease  on  the  nerves  of  the  hip  is 
conveyed  to  the  spinal  cord ;  it  is  thence  transferred  to  the 
central  termination  of  the  nerve  fibres  of  the  knee  joint ; 
through  these  the  impression  is  conducted  to  the  brain,  and 
the  mind,  referring  the  sensation  to  the  part  from  which  it 
is  accustomed,  through  these  nerves,  to  receive  impressions, 
feels  as  if  the  pain  were  in  the  knee.  In  the  same  way, 
when  the  sun's  rays  fall  strongly  on  the  retina,  a  tickling 
may  be  felt  in  the  nose,  causing  sneezing ;  or  irritation  in 
any  part  of  the  respiratory  organs  gives  rise  to  a  sensation 
of  tickling  in  the  glottis,  and  produces  coughing.  Wiien 
an  impression  received  at  a  nervous  centre  is  transferred  to 
many  other  fibres  in  the  same  centre,  it  is  said  to  be  dif- 
fused,   the  sensation  extending  far  beyond  the  part  from 


REFLEX  ACTION. 


295 


■ay, 
ing 

in 
ion 
len 

to 
lif- 
lorn 


whicli  the  primary  impression  proceeded,  as  is  seen  in  tooth- 
ache, in  which  the  adjoining  teeth  and  surrounding  parts 
are  similarly  aftected.  The  pain  caused  by  the  presence  of 
a  calculus  in  the  ureter  or  bladder,  is  diffused  far  and  wide. 

Reflection  or  Reflex  Action. — The  reflection  of  im- 
pressions exhibits  an  important  function  common  to  all  ner- 
vous centres,  and  is  the  source  of  all  reflex  moA  eraents.  The 
preceding  examples  are  all  instances  of  reflecMon,  or  reflex 
action,  for  the  manifestation  of  which  three  conditions  are 
necessary.  First,  sensitive  nerve  flbres,  to  convey  an  im- 
pression. Secondly,  a  nervous  centre,  to  which  the  im- 
})ression  may  be  conveyed,  and  in  which  it  may  be  reflected. 
Thirdly,  motor  nerve  flbres,  upon  which  this  impression  may 
be  conducted  to  the  contracting  tissue  (Fig.  104).  If  any  of 
these  conditions  be  absent,  a  proper  reflex  action  cannot  take 
place.  They  are  all  involuntary,  and  in  health  they  have  a 
distinct  purpose  L  subserve  in  the  animal  economy,  as  in 
the  movements  of  the  intestines,  the  respiratory  organs,  con- 
traction of  the  pupils,  closure  of  the  glottis,  etc. ;  but  in 
disease  many  of  them  are  irregular  and  purposeless,  as  in 
chorea,  convulsions,  etc.  Reflex  actions  may  be  divided  into 
primary,  and  secondary  or  acquired.  As  instances  of  the 
former,  may  be  mentioned  sucking  in  infants,  contraction  of 
the  pupil,  etc. ;  and  of  the  latter,  walking,  reading,  and 
writing. 

Nerve  Force  (vis  nervosa). — The  special  endowment  by 
which  nerves  act  and  manifest  their  vitality  is  a  peculiar 
one  inherent  in  the  structure  and  constitution  of  the  nervous 
substance.  It  manife,sts  itself  in  its  effects  on  the  muscles, 
in  sensation,  secretion,  excretion,  nutrition,  etc.  Nervous 
force,  though  not  identical,  presents  many  points  of  resem- 
blance to  Voltaic  electricity.  For  the  production  of  the 
latter,  the  ordinary  requisites  are  two  dissimilar  metals,  as 
zinc  and  platinum  or  copper,  and  an  interposed'  compound 
fluid,  as  dilute  sulphuric  acid.  When  these  metals  are 
placed  in  contact    with  each  other,  chemical   action  com- 


T 


296 


THE  NERVOUS  SYSTEM. 


c 
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L 


CSV 


mences,  a  current  sets  in  a  definite  direction,  and  a  state  of 
'polarity  or  electrical  tension  is  produced.  The  produc- 
tion of  nervous  force,  or  nervous  polarity,  may  have  as  anal- 
ogues two  kinds  of  nervous  matter,  cells  and  fibres,  and 
the  presence  of  a  fluid. 

From  the  structure  and  peculiarity  of  the  nervous  centres, 
there  is  much  to  justify  the  opinion  that  each  nerve  vesicle, 
and  fibre  connected  with  it,  together  with  the  blood-vessels 
and  fluid  surrounding  them,  is  a  distinct  apparatus  for  the 
"development  of  nervous  polarity.  The  whole  nervous  sys- 
tem is  therefore  in  a  constant  state  of  nervous  polarity,  and 
is  prepared  at  any  moment  to  receive,  conduct,  or  communi- 
cate impressions,  or  convey  motor  impulses.  A  slight  me- 
chanical or  chemical  stimulus  to  a  nerve,  is  capable  of  pro- 
ducing in  it  a  state  of  polarity,  and  rendering  it  capable  of 
conducting  impressions  or  motor  impulse ;  e.  g.,  pain  is  ex- 
cited by  touching  a  sensitive  nc^ve,  and  contractions  may 
be  produced  by  irritating  the  motor  nerve  of  an  amputated 


limb. 


THE  SPINAL  CORD. 


The  spinal  cord  is  n  cylindrical  column  of  nerve  substance, 
connected  above  wii  i  the  brain,  through  the  medulla  ob- 
longata, and  terminati  lielow — opposite  the  first  or  second 
lumbar  vertebra — in  a  slender  filament  of  grey  substance, 
{\\Q  filunn  terminale,  which  lies  among  the  leash  of  nerves 
forming  the  cauda  equina.  It  presents  two  enlargements, 
one  in  the  cervical  region,  extending  from  the  third  cervical 
to  the  first  dorsal  vertebra,  and  the  other  in  the  lumbar,  op- 
posite the  last  dorsal  or  first  lumbar.  The  spinal  cord  con- 
sists of  two  symmetrical  halves,  united  in  the  middle  line 
by  a  commissure.  They  are  separated  in  front  and  behind 
by  a  vertical  fissure,  the  posterior  fissure  being  deeper,  but 
narrower  than  the  anterior.  On  each  side  of  the  anterior 
fissure,  a  linear  series  of  foramina  may  be  seen,  from  which 
emerge  the  anterior  roots  of  the  spinal  nerves ;  this  is  the 


STRUCTURE  OF  THE  CORD. 


297 


irce, 
ob- 
2ond 
mce, 
•ves 
mts, 
deal 
op- 
Icoa- 
Jline 
bind 
I  but 
trior 
lich 
the 


BO-called  anterior  lateral  Jiaaare  of  the  cord.  On  each  side, 
near  the  posterior  part  of  tlie  cord,  and  corresponding  with 
the  posterior  roots  of  the  spinal  nerves,  may  be  seen  a  deli- 
cate fissure,  the  posterior  lateral  fissure.  On  each  side,  n,nd 
near  the  posterior  fissure,  is  a  sli^-ht  longitudinal  furrow — 
the  posterior  rtiedio-lateral  fissttre.  These  fissures  divide 
each  half  of  the  cord  into  four  columns,  anterior,  lateral, 
posterior  and  posterior  median  columns.  The  anterior  col- 
umn is  situated  between  the  anterior  median  and  the  ante- 
rior lateral  fissures.  It  is  continuous  with  the  anterior  pyr- 
amid of  the  medulla  oblongata,  in  which  decussation  of  the 
anterior  columns  takes  place.  The  lateral  column  is  situ- 
ated between  the  anterior  laterals nd  posterior  lateral  fissures, 
and  is  continuous  above  with  the  lateral  tract  of  the  medulla. 
The  posterior  column  is  situated  between  the  posterior 
lateral  and  the  posterior  medio-lateral  fissures,  and  is  con- 
tinuous with  the  restiform  body  of  the  medulla.  The  2)ost- 
erior  median  column  is  a  narrow  segment  situated  between 
the  posterior  medio-lateral  and  the  posterior  median  fissures, 
and  is  continuous  above  with  the  posterior  pyramid  of  the 
medulla  oblongata. 

Structure  of  the  Cord. — The  cord  consists  of  fibrous 
and  vesicular,  or  white  and  grey  nervous  substance  ;  the 
former  is  more  extensive,  and  situated  externally  ;  the  latter 
occupies  the  centre,  and  consists  of  two  crescentic  masses, 
connected  together  by  a  transverse  band,  the  gray  commis- 
sure. In  the  centre  of  this  commissure,  and  extending  the 
whole  length  or  the  cord,  is  a  minute  canal  lined  by  colum- 
nar ciliated  epithelium,  which  communicates  above  with  the 
fourth  ventricle.  Both  in  front  of  and  behind  the  gray 
commissure  is  a  transverse  band  of  white  substance,  the 
anterior  and  posterior  white  commissures;  these  connect 
the  white  substance  of  each  lateral  half  of  the  cord,  and 
form  the  floor  of  the  anterior  and  posterior  median  fissures 
respectively.  Each  crescentic  mass  of  gray  matter  presents 
an  anterior  and  a  posterior  horn ;  the  former  is  short  and 


298 


THE  NERVOUS  SYSTEM 


4-; 

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Mr> 


thick,  and  does  not  quite  reach  the  anterior  lateral  fissure  ; 
the  latter  is  long  and  slender,  and  extends  to  the  posterior 
lateral  fissure.  The  anterior  roots  of  the  spinal  nerves  are 
connected  with  the  anterior  horn,  and  the  posterior  roots 
with  the  posterior  horn.     The  white  substance  of  the  cord 


A,  the  anterior  median  fissure;  B,  jiostorior  median  fissure  ;  C, 
anterior  lateral  depression,  over  which  the  anterior  nerve-roots 
are  seen  to  spread  ;  D,  posterior  lateral  ffroovc,  into  which  the 
posterior  roots  are  seen  to  sink  ;  JO,  anterior  roots  passinff  the 
(janfflion  ;  k,  the  anterior  root  divided  ;  F,  the  i)osterior  roots, 
the  fihres  of  which  pass  into  the  ganglion;  G,  the  united  or  com- 
pound nerve,  and  its  division  into  anterior  and  posterior  branches. 

consists  of  transverse,  oblique,  and  longitudinal  nerve  fibres, 
blood-vessels  and  areolar  tissue  ;  and  the  gray  substance 
consists  of  smaller  nerve  fibres,  nerve  cells,  blood-vessels, 
and  delicate  areolar  tissue  (neuroglia).  There  are  a  number 
of  large  multipolar  nerve  cells  in  the  anterior  and  posterior 
cornu,  and  also  midway  between  the  two  cornu,  near  the 
external  surface  of  gray  matter. 

Spinal  Nerves. — The  spinal  nerves  consist  of  thirty-one 
pairs,  issuing  from  the  sides  of  the  whole  length  of  the 
cord.  Each  nerve  arises  by  two  roots,  an  anterior  or  motor, 
and  a  posterior  or  sensitive.  The  posterior  root  is  larger 
than  the  anterior  root,  (except  the  first),  and  has  a  ganglion 
developed  on  it  (Fig.  105).  Immediately  beyond  this  gan- 
glion the  two  roots  coalesce,  and  the  trunk  thus  formed 
passes  through  the  intervertebral  foramen,  after  which  it 
again  divides  into  two  branches,  an  anterior,  which  supplies 
the  anterior  surface  of  the  body  and  the  extremitie.s,  and  a 
posterior,  which  supplies  the  posterior  part  of  the  body, 
each  branch  containing  fibres  from  both  roots.  The  ante- 
rior roots  arise  from  the  antero-lateral  columns,  and  are  also 


FUNCTION  OF  THE  SPINAL  CORD. 


299 


rty-one 
of  the 
jmotor, 
larger 
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Is  gan- 
lormed 
licli  it 
[pplies 
and  a 
[body, 
I  ante- 
also 


connected  with  the  anterior  horn  of  the  gray  substance,  and 
the  multipolar  cells  found  connected  with  it ;  and  the  post- 
erior roots  arise  from  the  posterior  part  of  the  lateral  col- 
umn and  the  posterior  horns  of  the  gray  substance ;  the 
former  consist  exclusively  of  motor  fibres,  and  the  latter 
exclusively  of  sensitive  fibres. 

Function  of  the  Spinal  Cord. — The  spinal  cord  trans- 
mits impr  ssions  from  the  periphery  to  the  brain,  and  also 
enables  the  latter  to  bring  into  action  the  motor  nerves. 
Division  of,  or  injury  to  the  spinal  cord,  causes  an  interrup- 
tion of  voluntary  motion  and  sensation  in  those  parts  sup- 
plied by  nerves  below  the  part  affected,  while  the  functions 
of  the  parts  above  remain  unimpaired.  But  though»the  in- 
fluence of  the  brain  in  receiving  sensation,  and  exciting  vol- 
untary motion  is  cut  otF  or  interrupted,  the  portions  of  the 
cord  below  the  affected  part  still  possess  excito-motor  action, 
and  hence  the  cord  may  be  regarded  as  a  nervous  centre ; 
for  example,  in  cases  of  paralysis,  muscular  action  may  be 
excited  by  tickling  the  palms  of  the  hands,  or  soles  of  the 
feet  with  a  feather.  It  has  been  shown,  by  experiment, 
that  irritation  to  the  anterior  columns  of  the  cord  is  fol- 
lowed by  convulsive  movements  of  all  the  parts  supplied 
with  motor  nerves  below  the  irritated  part,  but  no  signs  of 
pain  are  manifested ;  while  irritation  of  the  posterior  col- 
umns appears  to  cause  excruciating  pain,  without  producing 
any  muscular  movement  besides  such  as  may  be  produced 
by  the  will  or  reflection.  Again,  when  the  spinal  cord  is 
completely  severed,  irritation  of  the  posterior  columns  of 
the  severed  part  produces  no  effect ;  but  irritation  of  the 
anterior  columns  is  followed  by  violent  movements.  On 
the  other  hand,  irritation  of  the  posterior  columns  of  the 
portion  of  the  cord  connected  with  the  brain  causes  acute 
pain  and  reflex  movements  ;  while  irritation  of  the  anterior 
columns  of  the  same  produces  no  effect.  Again,  when  both 
anterior  columns  alone  are  divided,  the  power  of  voluntary 
motion  is  lost  in  parts  below,  the  sensibility  remaining  per- 
17 


300 


THE  NERVOUS  SYSTEM. 


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c 

I. 

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m. 

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I. 

"v 

& 


IW  ■ 

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till  . 


feet ;  and  when  both  posterior  columns  are  divided,  sensation 
is  lost  in  the  parts  below,  the  power  of  motion  remaining 
unimi)aired.  From  this  it  would  appear  that  the  anterior 
columns  are  motor,  and  the  posterior  sensitive ;  nevertheless, 
the  result  of  injuries,  and  disease  of  different  parts  of  the 
cord,  arc  not  always  in  accordance  with,  but  in  some  in- 
stances directly  contrary  to  it  ;  for  example,  cases  have  been 
seen  in  which  comi)lete  loss  of  motion  occurred  without  any 
impairment  of  sensation,  as  the  result  of  lesion  of  the  pos- 
terior columns  of  the  cord,  the  anterior  being  wliolly  intact. 
Injuries  to  the  posterior  columns  are  invariably  attended 
with  hyperoisthesia  (Brown-Sequard). 

The  spinal  cord  has  a  crossed  action  for  both  motion  and 
sensation ;  for  example,  in  cerebral  apoplexy  the  paralysis 
and  loss  of  sensation  are  always  on  the  side  opposite  to  that 
on  which  the  lesion  has  taken  place.  The  decussation  of 
the  fibres  of  motion  occurs  between  the  anterior  pyramids 
of  the  medulla  oblongata  and  the  opposite  lateral  columns  of 
the  cord  and  may  be  seen  with  the  naked  eye,  (Fig.  105). 
The  discovery  of  the  crossed  action  for  sensation  is  due  to 
Brown  Sequard.  His  experiments  show  that  a  decussation 
•of  sensitive  impressions  takes  place  between  the  posterior 
columns  throughout  the  whole  extent  of  the  cord.  The 
sensitive  impressions  reaching  the  cord,  ascend  for  a  short 
distance,  and  ultimately  pass  across  to  the  opposite  side  of 
the  spinal  cord  to  reach  the  brain,  so  that  if  the  posterior 
column  of  one  side  be  impaired,  sensation  is  lost  on  the  op- 
posite side  of  the  body. 

The  spinal  cord,'as  a  nerve  centre,  or  aggregate  of  many 
nervous  centres,  has  the  power  of  conducting  and  commu- 
nicating or  transferring  impressions  received,  and  of  ex- 
Jiibiting  rejiex  action.  The  two  former  have  been  already 
referred  to  in  a  general  way.  Impressions  are  conducted 
through  the  gray  matter  of  the  cord,  there  being  in  all  pro- 
bability, separate  parts  for  conducting  motor  and  sensory 
impressions.     The  spinal  cord  does  not  posess  any  power  of 


isation 
mining 
.nterior 
theless, 
of  the 
me  in- 
^e  been 
)ut  any 
,he  pos- 
r  intact, 
ttended 

ion  and 
aralysis 
3  to  that 
lation  of 
yramids 
iumns  of 
ig.  105). 
due  to 
ssation 
(osterior 
The 
short 
side  of 
losterior 
the  op- 
many 
XommU' 
of  ex- 
ilready 
Wucted 
ill  pro- 
^ensory 
)wer  of 


FUNCTION  OF  THE  SPINAL  CORD. 


801 


autorruUic  or  independent  action,  like  the   higher   nerve 
centres. 

The  reflex  function  oi  the  spinal  cord  is  essentially  similar 
to  that  of  all  the  other  nervous  centres,  and  may  or  may 
not  be  under  the  control  of  the  will.  In  health  the  will  can, 
in  a  great  degree,  control  and  prevent  the  development  of 
reflex  actions  in  the  extremities.  If  ou^  of  the  leffs  be 
paralyzed,  as  in  hemiplegia  from  disease  of  the  brain, 
and  a  stimulus  be  applied  to  the  sole  of  the  foot  in  the 
paralyzed  limb,  reflex  actions  are  readily  produced  ;  but  on 
applying  the  same  stimulus  to  the  sound  limb,  no  such 
movements  occur,  the  patient  being  able  to  resist  the  ten- 
dency to  action  which  it  produces.  In  cases  of  paraplegia 
from  disease  of  the  spinal  cord,  even  where  the  loss  of  motion 
and  sensation  is  complete,  patients  are  sometimes  tormented 
with  involuntary  movements  of  the  lower  extremities  at 
night,  which  not  only  prevent  sleep,  but  also  occasion  pain 
and  distress.  It  is  no  doubt  caused  by  irritation  at  the  seat 
of  the  lesion. 

The  reflex  action  of  the  spinal  cord  is  essentially  involun- 
tary ;  for  example,  the  respiratory  movements  are  performed 
while  the  mind  is  occupied,  or  during  sleep  or  anaesthesia ; 
yet,  the  mind  can  by  a  voluntary  act  direct  and  strengthen 
them,  and  adapt  them  to  the  several  acts  of  _j)eech,  effort, 
etc.  Some  reflex  actions  may  be  controlled,  or  entirely  pre- 
vented by  the  will,  which  thus  exercises  an  inhibitory  action 
over  them ;  for  example,  when  the  sole  of  the  foot  is  tickled 
we  can  by  an  act  of  the  will  control  the  reflex  action  which 
it  occasions.  When  the  limb  is  pinched  or  pricked,  it  is  in- 
voluntarily withdrawn  from  the  instrumentof  injury,and  the 
e3'e  is  involuntarily  closed  when  a  blow  on  the  face  is  threat- 
ened; but  both  these  reflex  actions  may  be  controlled  by  an 
effbrtof  the  will.  Many  reflex  actions  are  entirely  involuntary 
as  for  example,  the  contraction  of  the  pupil,  the  movements 
of  the  intestines  (except  defecation),  the  action  of  the  uterus 
in  parturition,  etc. 


302 


THE  NERVOUS  SYSTEM. 


c 
t 

n 
I. 

I' 

»• 

«\ 


«1 

II- 

ini ' 
•»> 

KKX 


The  spinal  cord,  with  its  encephalic  prolongation,  may  be 
said  to  supply,  by  its  reflex  power,  the  conditions  requisite 
for  the  maintenance  of  the  various  muscular  movements 
which  are  essential  to  the  continuance  of  the  organic  pro- 
cesses ;  and,  as  Marshall  Hall  has  pointed  out,  it  especially 
governs  the  various  orifices  of  ingress  and  egress.  Thus, 
the  act  of  deglutition  is  entirely  dependent  on  the  spinal 
axis  (medulla),and  the  nerves  proceeding  from  it.  The  action 
of  the  cardiac  and  pyloric  orifices  of  the  stomach  is  wholly 
regulated  without  the  consent  of  the  will.  The  movements 
of  the  intestines  are  influenced  by  the  spinal  cord  through 
the  sympathetic  system.  The  sphincter  ani  and  sphincter 
vesicae  are  under  its  influence,  although  partly  subject  to 
the  control  of  the  will.  The  reflex  action  of  the  spinal 
cord  is  also  exhibited  in  the  ex])ulsion  of  the  generative 
products  as  the  semen,  in  defecation,  micturition,  and  in  par- 
turition in  its  second  stage. 

The  phenomena  of  spinal  reflex  action  in  man  are  more 
marked  in  disease  than  in  health  ;  e.  g„  in  tetanus  a  slight 
touch  on  the  skin,  or  a  breath  of  air,  is  sufficient  to  throw 
the  whole  body  into  convulsions  ;  a  similar  state  is  induced 
by  the  introduction  of  strychnine  or  opium  in  frogs.  In 
these  instances,  the  spinal  cord  is  in  a  state  of  polar  excite- 
ment, and  is  kept  so  b}'  the  constant  irritation  propagated 
to  it  by  the  wounded  part,  on  the  one  hand,  or  the  poison- 
ous substance  circulating  in  the  blood,  on  the  other,  there 
being  no  inflammatory  or  congested  condition  either  of  the 
cord  or  its  membranes. 

The  spinal  cord  is  constantly  in  activity  ;  in  all  periods 
and  phases  of  life,  the  movements  which  are  essential  to  its 
continued  maintenance  are  kept  up  without  sensible  effort. 
"  The  spinal  system  never  sleeps  ;  "  it  is  the  brain  alone 
which  is  torpid  during  sleep,and  whose  functions  are  affected 
by  this  torpidity.  It  has,  however,  its  periods  of  momen- 
tary rest,  similar  to  other  organs  of  the  body,  as  the  heart, 
lungs,  etc.,  which  appear  to  be  constantly  in  action. 


ENCEPHALON. 


303 


more 


jriods 
I  to  its 
iifort. 
lalone 
lected 
imen- 
leart, 


Ki''.  10(1 


ENCEPHALON. 

The  encephalon  is  situated  in  the  cranial  cavity,  and 
consists  of  the  medulla  oblongata,  'pons  Varolii,  cerebellum 
and  cerebrum. 

Medulla  Oblongata. — The  medulla  oblongata  is  the 
cephalic  prolongation  of  the  spinal  cord,  and  connects  it  with 
the  brain.  It  is  larger  than  the  spinal  cord,  and  is  divided 
into  segments,  which  are  continuous  with  the  columns  of 
the  spinal  cord  below.  It  is 
separated  into  two  lateral 
halves  by  fissures,  which  cor- 
respond with  the  anterior 
and  posterior  fissures  of  the 
cord  ;  and  each  lateral  half  is 
again  subdivided  by  minor 
grooves  into  four  columns, 
the  anterior  pyramid,  lateral 
tract  and  olivary  body,  resti- 
forvibody  a.nd  posterior  pyra- 
mid. These  are  continuous 
with  the  anterior,  lateral, 
posterior,  and  posterior  me- 
dian columns  of  the  spinal 
cord  respectively. 

Structure. — ThQanterior 
pyramid  is  c  omposed  entirely 

*;  '  ^  Aiitoriui-  view  of   thu   iiieilulla  •.lilon.;ata 

of   white  fibres  derived  from    'i'"'  I'O"**  Viuoiii.  \.  infuiuiibuiuin ;  •>.,  tuber 

fiiiureum ;  3,  corpora  albicaiitia  ;  4,  cerebral 
the    anterior     column     of    the     r<=rtuncle  ;  5,  pons  varolii ;  e,  origin  of  the 

middle  peduncle  of  the  cerebellum  ;  7, 
cord  of  its  own  side,  and  from     nntcriormiramUho/themedulla oblongata; 

8,  decussation  of  the  anterior  pyramids; 
the     lateral     C   lumns     of     the     ^'   'I'^^^'J/  bodies  ,•  lO,  rcsti/orm  bodies ;  11, 

arci/orm  fibres;  12,  upper  extremity  of  the 

opposite  half  of  the  OOrd,  and     ^P"',*1  «=°'''1  -.l^,  liga-uentum  denticulatum  ; 
'^  '■  '14,  dura  mater  of  the  cord  ;  Ifi,  optic  tracts  ; 

is     continued     upwards      into     1«.  "Ptic  conimlssure  or  chiasni ;  17.  motor 
r  .V  ..        ociili  ;  IS,  ])athetic  ;  If),  fifth    nerve  ;  20,  ab- 

the  eerebrnm  and  PPrpbplbim       dni-'ons  ;  21,   facial;   22,  auditory  ;  (2:5,  nerve 
tue  V^eieuiumdUU  CCieueiiUm.     ^f    Wrlsberg);   24,    glosso-pharyngeal ;    25, 

Thp      PPrpbpllnr      fil-»rp«      i->n>a«     pneumogastric;  2(i,  2C,  spinal  accessory  ;  27, 
±lie       Leieueildl       noreS      pass     hypoglossal ; 28, 21),  cervical  nerves.  (Sappcy). 

beneath   the   olivary  body,  join    the   restiform  body  and 


sot 


THE  NERVOUS  SYSTEM. 


c 
c 

c 

L 

!• 

•I 

m, 

I 


•  IV' 

n«'. 
(«. 


spread  out  in  tho  corobelluin;somo  of  the  cerebral  fibres  in- 
close the  olivary  body  and  enter  the  pons  as  the  olivary  fas- 
ciculus, but  the  niasH  of  the  fibres  enter  the  pons  Varolii  in 
their  pansage  upwards  to  the  cerebrum.  The  decussation 
between  the  anterior  pyramids  n»ay  bo  distinctly  seen  with 
the  naked  eye. 

Tiie  lateral  tract  is  continuous  with  the  lateral  column  of 
the  cord.  Its  fibres  pass  in  three  different  directions  ;  the 
external  join  the  restiform  body,  and  pass  to  the  cerebellum^ 
the  internal  pass  forwards,  pushing  aside  the  fibres  of  the 
anterior  column,  and  form  part  of  the  o[)posite  anterior 
pyramid,  and  the  middle  fibres  ascend  to  the  cerebrum, 
forming  thii  fasciculi  teretes  in  the  floor  of  the  fourth  ven- 
tricle. The  olivary  body  presents  on  a  transverse  section, 
a  whitish  substance  externally,  and  a  grayish-colored  body 
in  the  interior — the  corpus  deniatum — which  presents  a  zig- 
zag outline,  and  contains  some  white  substance  in  the  in- 
terior, which  communicates  with  that  on  the  external  sur- 
face by  means  of  an  aperture  in  its  posterior  part. 

The  restiform  body  is  continuous  below  with  the  posterior 
column  of  the  cord,  and  receives  some  fibres  from  the  lateral 
and  anterior  columns  ;  superiorly,  it  divides  into  two  fasci- 
culi ;  the  external  one  enters  the  cerebellum ;  the  internal 
one  joins  the  posterior  pyramid,  and  blends  with  the  fasci- 
culi teretes  as  it  passes  up  to  the  cerebrum. 

The  i>osterior  'pyramids  are  continuous  with  the  posterior 
median  columns  of  the  cord.  Opposite  the  apex  of  the  floor 
of  the  fourth  ventricle,  they  present  an  enlargement  {i^ro- 
cess  clavatus),  and  diverging,  form  the  lateral  boundaries  of 
the  calamus  scriptorium.  They  then  join  the  external  fas- 
ciculus of  the  restiform  bodies,  and  pass  with  them  up  to 
the  cerebrum. 

In  the  lower  part  of  the  medulla  the  gray  matter  is  ar- 
ranged as  in  the  cord  ;  but  in  the  upper  part  it  becomes 
more  abundant,,  and  is  disposed  apparently  with  less 
regularity. 


FUNCTION  OF  THE  MEDULLA  OBLONGATA.    8C5 


jsof 
fas- 
to 


ar- 

Imes 
less 


Function  of  the  Medulla  Ohlongata. — The  general 
function  of  the  medulla  oblongata  is  similar  to  that  of  the 
spinal  cord.  It  may  be  regarded  as  a  conductor  of  impres- 
sions, in  which  respect  it  has  a  wider  extent  of  function  than 
any  other  part  of  the  nervous  system,  since  all  impressions 
between  the  brain  and  spinal  cord  ])ass  through  it.  In  con- 
sequence of  the  decussation  of  the  anterior  pyramids,  motor 
impressions  proceeding  from  the  bra?  i  \  pass  across  to  the  op- 
posite side  of  the  spinal  cord ;  for  example,  in  injury  to  one 
side  of  the  head,  producing  paralysis,  the  loss  of  motion  is 
always  on  the  side  opposite  to  that  on  which  the  injury  was 
received. 

Besides  the  function  of  conduction,  the  medulla  oblongata, 
acting  as  a  nervous  centre,  presides  over  the  functions  of 
respiration,  deglutition,  etc.  The  brain  of  the  lower 
animals  may  be  wholly  removed  above,  ano  yet  life  maj' 
continue,  and  the  respiratory  function  be  carried  on.  The 
same  is  the  case  when  the  spinal  cord  below  the  phrenic 
nerve  is  removed  ;  and  even  when  both  the  brain  and  spinal 
cord  are  removed,  the  function  of  respiration  may  be  con- 
tinued ;  but  whenever  the  medulla  is  wounded  the  function 
is  instantly  arrested,  and  the  animal  dies  as  if  asphyxiated. 
The  medulla  oblongata  may  continue  to  discharge  its  func- 
tions as  a  nervous  centre  after  the  power  of  conduction  has 
ceased  to  act ;  thus,  in  coma  from  apoplexy  or  compression, 
and  in  antesthesia  from  ether  or  chloroform,  patients  con- 
tinue to  breathe,  although  they  are  wholly  insensible.  The 
reflex  action  of  the  medulla  is  peculiar  from  having  a  very 
wide  range  of  connection.  The  principal  centripetal  nerves 
engaged  in  respiration  are  the  pneumogastrics;  but  that  these 
are  not  the  only  ones  may  be  shown  by  their  division  when 
respiration  becomes  slower,  but  is  not  arrested.  The  wide 
range  of  connection  which  belongs  to  the  medulla  is  further 
shown  by  the  fact  that  impressions  on  the  surface  of  the 
body  may  induce  respiratory  movements,  as  e.g.,  dashing 


306 


THE  NERVOUS  SYSTEM. 


L 


Us 


// 


cold  water  on  the  face  or  body  is  instantly  followed  by  a 
deep  inspiration. 

From  the  medulla  arise  the  movements  required  in  the 
act  of  deglutition.  This  may  be  shown  by  the  persistence 
of  the  power  of  deglutition  after  the  removal  of  the  cere- 
brum and  cerebellum,  and  by  its  complete  arrest  when  the 
medulla  is  injured.  The  reflex  power  of  the  medulla  in  de- 
glutition is  much  simpler  and  more  restricted  than  in  re- 
spiration. It  is  also  the  centre  for  the  movements  required 
in  speech  anc*  *Tiastication ;  for  the  special  senses  of  hearing 
and  taste  ;  for  regulating  the  action  of  the  heart  (p.  212) ;  the 
action  of  the  iris  and  ciliary  muscle ;  and  the  secretion  of  the 
saliva.  It  is  likewise  the  chief  vaso-motor  centre  from 
which  fibres  pass  down  the  cord,  accompanying  the  spinal 
and  sympathetic  nerves,  and  are  distributed  to  the  blood- 
vessels (p.  219.)  The  gray  matter  in  the  floor  of  the  fourth 
ventricle  when  irritated  produces  glycosuria,  and  is  there- 
fore called  the  diabetic  centre  (p.  151.)  This  is  probably 
tlie  result  merely  of  stimulating  the  vaso-motor  centre. 

Pons  Varolii. — The  pons  Varolii,  meso-cephalon  or 
tuber  annulare,  is  the  bond  of  union  between  the  cerebrum, 
cerebellum,  and  medulla  oblongata.  In  structure  it  consists 
of  longitudinal  and  transverse  fibres,  intermixed  with  gray 
matter.  The  longitudinal  fibres  are  continued  up  through 
tlie  pons  from  the  anterior  pyramids,  olivary  bodies,  lateral 
and  posterior  columns  of  the  cord.  The  transverse  fibres 
connect  the  two  hemispheres  of  the  cerebellum,  forming  the 
transverse  commissure,  and  are  divided  into  a  superficial  and 
deep  layer  ;  the  former  passes  across  the  surface  of  the  pons, 
and  the  latter,  situated  deeply,  decussates  with  the  longi- 
tudinal fibres. 

Function  of  the  Pons  —It  acts  as  a  conductor  and  also 

as  a  nerve  centre.     As  a  conductor  it  is  the  channel  through 

v/hich  impressions  are  conveyed  from  the  spinal  cord  to  the 

.cerebrum  and  cerebellum,  and  also  between  the  two  hemi- 

jspheres  of  the  cerebellum.     It  is  the  nervous  centre  for  stasis 


ed  by  a 

d  in  the 
rsistence 
Aie  cere- 
hen  the 
la  in  de- 
ll in  re- 
required 
hearing 
12) ;  the 
)n  of  the 
;re  from 
e  spinal 
3  blood- 
e  fourth 
s  there- 
)robably 
tre. 

alon  or 

ebrum, 

consists 

th  gray 

irough 

lateral 

fibres 

ing  the 

ial  and 

e  pons, 

longi- 

d  also 
irough 
to  the 
hemi- 

stasis 


THE  CEREBELLUM. 


307 


find  progressiori,  and  may  also  be  regarded  as  the  connecting 
link  between  the  different  portions  of  the  encephalon,  for 
when  the  cerebrum  and  cerebellum  are  removed  in  one  of 
the  lower  animals,  it  may  still  have  sensation  of  painful  im- 
pressions and  power  of  motion,  (Vulpian.)  It  is  a  ner- 
vous centre  for  higher  and  more  definite  reflex  actions  than 
the  medulla  or  any  part  of  the  spinal  cord — reflex  actions 
of  an  emotional  and  instinctive  character. 

In  hemiplegia  from  disease  of  the  corpus  striatum,  there 
is  paralysis  on  the  opposite  side  of  the  body,  and  paralysis 
of  the  face  on  the  same  side  as  that  of  the  body  (cognate). 
This  shows  that  the  cranial  nerves  have  a  crossed  action  as 
well  as  the  spinal  nerves.  Unilateral  disease  of  the  pons 
Varolii  is  liable  to  involve  the  facial  nerve,  before  decussa- 
tion has  taken  place,  and  the  ]»aralysis  of  the  face  will  then 
be  on  the  opposite  side  to  that  of  the  body  (alternate). 
Hence  in  lesions  of  the  brain  above  or  in  front  of  the 
j)ons,  there  is  cognate  paralysis,  and  in  lesions  of  the  pons, 
iilternate  paralysis. 

Cerebellum. — The  cerebellum  consists  of  two  lateral 
herkiispheres  connected  together  by  a  trar  sverse  commissure 
or  band,  the  vermiform  process.  It  is  situated  in  the  pos- 
terior fossa  of  the  cranium,  beneath  the  ])osterior  lobes  of 
the  cerebrum,  from  which  it  is  separated  by  the  tentorium 
oerebelli.  It  is  oblong  in  shape,  measuring  from  three  and 
a  half  to  four  inches  transversely  ;  from  two  to  two  and  a 
half  from  before  backwards,  and  two  inches  in  thickness, 
and  weighs  from  five  to  six  ounces.  Each  hemisphere  is 
divided  into  several  lobes,  of  diffei'ent  sizes,  and  its  surface 
is  marked  by  numerous  curved  furrows  or  sulci,  which  vary 
in  depth  in  difierent  parts.  Its  surface  is  covered  by  the 
pia  mater. 

Structure. — It  consists  of  gray  and  white  matter  ;  the 
former,  darker  than  that  of  the  cerebrum,  occupies  the  sur- 
face ;  the  latter  the  interior.  When  divided  vertically  it  is 
•seen  to  consist  of  a  central  stem  of  white  matter,  which  con- 


.M08 


THE  NERVOUS  SYSTEM. 


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c 

I. 
I- 

■1; 
•». 


f 


Si;;. 

tnr 


tains  in  its  interior  a  frrayisli  mass— tlio  corpus  «lontatuni. 
Tho  central  stoni  of  white  matter  sends  fortli  laminae  towards 
the  surface,  whicli  are  surrounded  by  tlie  j?ray  matter  so  thai 
<lie  cut  surfaco'of  tho  orj^nn  presents  a  foliated  ajipearanee 
to  which  tlu?  name  arbor  vita>  has  been  given.  A  vertical 
"•^  '"'  section  of  the   ^M-ay  matter   or   cortical 

substance  [)>osents  the  following  apjx^ar- 
ance.  Externally  is  a  thick  layer  of  fine 
connective   tissue   in    which  is   seen  a 
luntiber   of    splierical     corpuscles    like 
those  of  the  granular  layer  of  the  retina; 
n(>xt  is  a  single  layer  of  branched  nerve 
cells  (cells  of  Varkivjc)  i\w  branches  of 
which  |)ass  u|)wards  into  the  external 
i:^  layer   and    blend    with    the  corpuscles, 
U  and  some   single  branches  downwards. 
■(i5>5.   Heneath  this  is    tho   so-called   granular 
Si^   layer  which  cousists  of  a  dense  layer  of 

rounded     cprjniscles,     resembling     tho 

voriI7rtr^i^r!7,-^s  luiclear  layer  of  the  retina  ;  and  lastly  a 
k'^^ISus";.;'":;-  'r;:;uh!]o  I  l'»y«i-  of  "^>-ve  fibres  with  a  tew  scattered 
pl-iXlM  C.'r'or;,;;';';;  coVpuscles ;  this  layer  partly  belongs  to 
.ibm.witba  v.n.  ..ut,o,v.i  ^|^,,  ^^,,,5^^  substanco. 

The  cerebellum  is  connected  with  the  rest  of  the  en- 
cephalon  by  processes  or  ]>rolongations,  called  peduncles. 
These  are  three  in  number,  tlie  superior,  middle  and  iii- 
fevior.  The  superior  2)ed uncles  connect  the  cerebellum 
with  the  cerebrum.  They  pass  ujnvards  beneath  the  testes 
to  the  crura  cerebri  and  optic  thalami.each  peduncle  forming 
part  of  the  lateral  boundar}'  of  the  fourth  ventricle.  Beneath 
the  corpora  quadrigemina  the  innermost  fibres  of  each  pe- 
duncle decussate  with  each  other,  some  fibres  from  one  side 
of  the  cerebellum  conununicating  with  the  opposite  side  of 
the  cerebrum.  The  middle  peduncles,  the  largest  of  the 
three,  connect  together  the  two  hemispheres  of  the  cere- 
bellum, and  form  the  transverse  fibres  of  the  pons  Varolii. 


FUNCTION  OF  THE  CEREBELLUM. 


300 


lirming 
iiieath 
3h  pc- 
side 
ide  of 
>f  the 
ccre- 
arolii. 


Tho  inferior  'pednnden  (crura  C(ircbelli)  comiocfc  the  core- 
b(ilhirn  with  tho  nioduUa  ohlon^^ata.  Tlioy  pass  clown  wards 
to  tho  l)ack  part  of  the  inodulla,  and  form  part  of  the  resti- 
form  hodios. 

FuNOTFON  01'"  TiiK  (Ikkkhkllum. — Tho  corcbcllum  is  in- 
sonsihle  to  irritation,  and  may  ho  cut  away  withotit  causinij 
pain  ;  but  if  any  of  the  crura  bo  toucliod,  pain  is  instantly 
felt.  Its  removal  is  not  attended  with  ai»y  loss  or  disorder 
of  sensibility  ;  tho  animal  can  soo,  hoar,  smell,  etc.,  as  before 
its  removal ;  but  ho  has  lost  tho  power  of  springing,  flying, 
walking,  standing,  etc.,  and  his  actions  are  like  those  of  a 
drunken  man.  The  action  of  its  two  lialv(!S  must  always 
bo  balanced,  for  if  oruvhalf  of  the  cerelxiJlum  be  removed,  or 
one  of  its  crura  dividocl,  the  animal  exhibits  a  tendency  to 
r.  ;ver  upon  its  longitudinal  axis,  and  from  the  side  in- 
jutv;vi.  From  the  above  circumstances  it  would  appear,  that 
the  function  of  tho  cerebellum  is  to  regulate  uTid  co-ordinate 
the  muscular  Tnovcmtnts  of  the  body.  The  influence  of 
each  half  of  the  cerebellum  is  directed  to  muscles  on  the 
opposite  side  of  the  body.  It  is  also  the  organ  through 
which  tho  mind  acquires  a  knowledge  of  the  state  and  posi- 
tion of  the  muscles,  and  exerts  a  will  upon  them — the  organ 
of  muscular  sense. 

The  ceiobellum  is  supposed  by  some  to  be  the  organ  of 
sexual  instinct,  or  of  amativeness.  The  facts  adduced  in 
favor  of  it  are — 1st,  cases  in  which  atrophy  of  tho  testes  and 
loss  of  sexual  passion  have  resulted  from  injuries  to  the 
cerebellum ;  2nd,  disease  of  the  cerebellum  has  been  attended 
with  almost  constant  erection  of  the  penis,  and  frequent 
seminal  emissions  ;  3rd,  that  it  has  seemed  possible  to  esti- 
mate the  degree  of  sexual  passion  in  different  animals  by 
the  conjparative  size  of  the  cerebellum.  In  reference  to  the 
first  class  of  facts,  the  loss  of  sexual  passion  may  have  been 
the  consequence  of  atrophy  of  the  testes,  and  hence  these 
facts  have  little  bearing  on  the  question,  unless  it  can  be 
shown  that  the  loss  of  sexual  passion  followed  the  injury  of 


SIO 


THE  NERVOUS  SYSTEM. 


c 
c 

I. 

tin 


f 

U 

itv< 


the  cerebellum,  before  the  testes  began  to  diminish.  Disease 
of  the  cerebellum  proves  nothing,  because  the  same  thing 
more  generally  occurs  in  diseaoe  of  the  medulla  and  spinal 
cord.  On  the  other  hand,  cases  are  recorded  in  which  the 
whole  of  the  cerebellum  has  been  disorganized,  or  completely 
absent,  without  loss  of  the  sexual  passion.  Besides,  among 
animals  there  is  no  proportion  between  the  size  of  the  cere- 
bellum and  the  development  of  the  sexual  passion,  and  cas- 
tration in  early  life  is  not  followed  by  any  diminution  of 
this  organ.  The  cerebellum  of  the  cock  is  no  larger 
than  that  of  the  hen,  although  the  sexual  passion  is  many 
times  greater.  The  cerebellum  in  frogs  and  toads  is  only  a 
small  bar  of  nerve  substance,  yet  the  sexual  instinct  is  very 
strong. 

The  Cerebrum. — The  cerebrum  occupies  the  upper  part 
of  the  cranial  cavity,  resting  upon  the  anterior  and  middle 
fossae  of  the  base  of  the  skull,  and  is  separated  posteriorly 
from  the  cerebellum  by  the  tentorium  cerebelli.  It  is  ovoid- 
al  in  shape,  and  is  divided  into  two  lateral  hemispheres, 
which  are  connected  together  by  a  broad  transverse  com- 
missure of  white  matter — the  corpus  callosum.  The  aver- 
age weight  of  the  brain  is  about  fifty  ounces  in  the  male, 
and  forty-five  in  the  female.  The  weight  of  the  brain  in- 
creases rapidly  up  to  the  seventh  year,  more  slowly  up  to 
twenty,  and  still  more  slowly  up  to  the  fortieth  year.  When 
it  reaches  the  maximum,  it  remains  stationary  for  a  few 
years,  and  then  declines  as  age  advances  about  one  ounce 
for  each  subsequent  decennial  period.  As  a  rule,  the  size  of 
the  brain  bears  a  general  relation  to  the  intellectual  capa- 
city of  the  individual.  The  brain  of  Cuvier  weighed  rather 
more  than  sixty-four  ounces ;  Dr.  Abercrombie  sixty-three; 
RulofF,  a  celebrated  linguist,  executed  for  murder  in  1879, 
fifty-nine  ;  James  Fisk,  Jr.,  fifty-eight ;  Spurzheim  fifty-five; 
Daniel  Webster,  fifty-three;  Agassiz,  fifty-three  ;  Dupuy- 
tren,  forty-nine  (Cruveilhier).  The  brain  of  the  Hon.  D'Arcy 
McGee,  the  celebrated  Canadian  statesman,  weighed  fifty- 


THE  CEREBRUM. 


311 


Disease 
me  thing 
id  spinal 
-^hich  the 
mpletely 
3,  among 
the  cere- 
and  cas- 
lution  of 
o  larger 
is  many 
is  only  a 
t  is  very 

)per  part 
d  middle 
isteriorly 
is  ovoid- 
ispheres, 
se  com- 
he  aver- 
male, 
rain  iu- 
up  to 
When 
a  few 
|e  ounce 
size  of 
d  capa- 
rather 
-three; 
1879, 
'■-five; 
Hipuy- 
'Arcy 
fifty- 


nine  ounces.  Cromwell's  brain  was  said  to  have  weighed 
eighty-two  ounces,  and  Byron's  seventy-nine  ;  but  these 
figures  are  not  generally  accepted  by  physiologists.  On  the 
other  hand,  the  brain  of  an  idiot  seldom  weighs  more  than 
twenty-three  ounces.  Wagner,  however,  mentions  a  case  of 
an  idiot  whose  brain  weighed  fifty-four  ounces,  and  Dr. 
Tuke  reports  a  case  in  which  the  brain  of  a  congenital  epi- 
leptic idiot  weighed  sixty  ounces,  but  these  are  exceptional. 
In  only  two  animals  is  the  brain  larger  than  in  man,  viz., 
the  elephant  and  the  whale. 

The  'mere  comparative  size  of  the  brain,  or  quantity,  how- 
ever, does  not  always  give  an  accurate  measure  of  the  am- 
ount of  mental  power,  for  not  unfrequently  men  possessing 
large  and  well-formed  heads  are  seen,  whose  mental  capa- 
bilities are  not  greater  than  those  of  others  whose  crania  have 
the  same  general  proportion,  but  are  much  smaller.  Large 
brains,  with  deficient  activity,  are  commonly  found  in  per- 
sons of  a  lymphatic  temperament ;  whilst  small  brains,  and 
great  activity,  characterize  the  sanguine  and  nervous  tem- 
peraments. The  quality  of  the  nerve  tissue  in  regard  to 
fineness  of  nerve  fibres,  and  cells,  the  degree  of  vascularity, 
and  the  number  and  extent  of  the  convolutions,  bear  an 
important  relation  to  the  intellectual  capacity  of  the  indi- 
vidual. 

Structure. — The  cerebrum  consists  of  two  kinds  of 
nerve  tissue,  the  gray  and  the  white ;  the  former  is  situated 
externally,  the  latter  internally.  The  surface  of  the  cere- 
brum presents  a  number  of  convolutions  or  foldings,  separ- 
ated from  one  another  by  depressions  or  sulci  of  various 
depths.  The  outer  surface  of  each  convolution  is  composed 
of  gray  matter,  which  is  sometimes  called  the  cortical  sub- 
stance, and  the  interior  consists  of  white  matter.  The  con- 
volutions are  admirably  adapted  to  increase  the  extent  of 
surface  or  amount  of  gray  matter,  without  occupying  much 
additional  space.  The  gray  matter  of  the  convolutions, 
when  closely  examined,  however,  appears  to  consist  of  from 


312 


THE  NERVOUS  SYSTEM. 


c 
c 

^ 

aw 


•-ti-*.. 


iour  to  six  layers  of  gray  and  white  tissue  placed  alternately, 
iVotn  two  to  three  layers  of  p;ray  substance,  and  an  equal 
number  of  white  ;  the  latter  occuj)ying 
the  surface.  A  vertical  section  of  these 
layers  presents  the  api)earance  represented 
in  the  accompanying  figure:  1st,  horizon- 
tal transverse  and  ol)lique  nerve  fibres ; 
2nd,  a  layer  of  fibres  with  a  few  nerve 
cells ;  3rd,  a  layer  with  numerous  cells  of 
different  shapes ;  4th,  a  layer  consisting  of 
pyramidal  cells,  with  their  bases  down- 
wards, characteristic  of  the  cerebrum;  they 
receive  two  processes  at  their  inferior 
extremity,  and  give  off  one  upwards,  and 
are  interspersed  among  radiating  nerve  fi- 
bres; 5th,  a  narrow  layer  with  irregular 
cells  like  those  of  the  cerebellum  ;  6th,  a 
broad  layer  with  irregular  and  fusiform 
cells.  The  sulci  are  generally  about  an 
inch  in  depth  ;  but  they  vary  in  different 
brains,  and  in  different  parts  of  the  same 
brain,  being  usually  deepest  on  the  outer 
surface  of  the  hemispheres.  The  convolu- 
tions of  the  brain  are  the  centre  of  intel- 
lectual action,  and  their  number  and  ex- 
tent and  the  depth  of  the  sulci,  bear  a 
close  relation  to  the  intellectual  power  of  the  individual. 
The}'  are  entirely  absent  in  some  of  the  lower  orders  of 
mammalia,  and  increase  in  number  and  extent  as  we  ascend 
the  scale.  The  largest  and  most  constant  convolutions  of 
the  human  brain  are  the  convolutions  of  the  corpus  cal- 
losum,  supra-orbital  convolutions,  and  the  convolutions  of 
the  longitudinal  fissure. 

Each  hemisphere  is  divided  into  five  lobes  :  the  frontal, 
(F),  'parietal  (P),  teraporo -sphenoidal  (T),  occipital  (O),  and 
central  lobe,   or  island  of  Reil,  which  are  separated  from 


Vertical  section  of  the 
cortical  substance  of  the 
cerebrum  ;  i)ni,  jiia 
mater  ;  c,  capillaries  ; 
nc,  nerve  cells  in  the 
neuroglia ;  pc,  pyrami- 
dal cells  (SehoflelU;. 


STRUCTURE  OF  THE  CEREBRUM. 


313 


M-natcly, 
n   equal 
:cui)ying 
3f   these 
resented 
horizon  ■ 
)   fibres ; 
w    nerve 
3  cells  of 
listing  of 
;s  down- 
ura ;  they 
inferior 
irds,  and 
nerve  fi- 
ir  regular 
n  ;  6th, a 
fusiform 
ibout   an 
different 
the  same 
ihe  outer 
couvolu- 
of  intel- 
and  ex- 
:i,  bear  a 
dividual, 
lorders  of 
e  ascend 
lutions  of 
•pus  cal- 
utions  of 

frontal, 
(O),  and 
Ited  from 


I'ach  other  by  the  following  fissures  :  the  fissure  of  Sylviua, 
i'^),  fissure  of  Rolando  (central  fissure)  (c),  and  parieto-occi- 


V,  frontal  loue  ;  F,  parietal  lobe  ;  I), occipital  lobe;  T,  temporo-spheiioiilal  lobe  ;  S,  fis- 
sure of  Sylvius ;  S',  horizontal,  S",  ascendiiifr  ramus  of  the  same  ;  c,  sulcus  centralis  (fis- 
sure of  Rolando) ;  f  1,  superior,  f2,  inferior  ;  f3,  praicentral  fissure  ;  ip,  interparietal  fissure ; 
po,  parieto-occipital  fissure ;  tl,  first ;  t2,  second  temporo-sphenoidal  fissures  (Eclier). 

pital  fissure  (po).  (Fig.  108.)  The  lobes  are  again  sub- 
divided into  lobules.  The  frontal  lobe  is  bounded  behind 
by  fissure  of  Rolando,  and  below  by  the  fissure  of  Sylvius ; 
the  parietal  lobe,  in  front  by  the  fissure  of  Rolando,  and  be- 
hind by  the  parieto-occipital  fissure,  which  in  man  appears 
as  a  notch  in  the  inner  margin  of  the  hemisphere  ;  the  tem- 
poro-sphenoidal lobe  is  situated  beneath  the  horizontal  branch 
of  the  fissure  of  Sylvius ;  the  occipital  lobe  is  situated  be- 
liind  the  parieto-occipital  fissure ;  and  the  central  lobe,  or 
island    of  Reil,  is  situated  upon  the  under  surface  of  the 


314 


THE  NERVOUS  SYSTEM. 


c 
c 

c 
I. 
^ 

■\ 

■HI. 
I 

6 


IBT' 


anterior  part  of  the  cerebrum  at  the  bifurcation  of  the  fis- 
sure of  Sylvius.  The  under  surface  of  the  frontal  lobe 
occupies  the  anterior  fossa  of  the  base  of  the  cranium,  the 
parietal  and  temporo-sphenoidal  the  middle  fossa,  and  the 
occipital  the  posterior  fossa.  They  were  formerly  named 
anterior,  middle,  and  posterior  lobes  respectively. 

The  figures  in  the  accompanyinjy  diagram  of  the  human 
brain  are  made  to  correspond  with  the  areas  of  the  brain  of 
the  monkey  as  determined  by  the  experiments  of  Ferrier, 
and  the  effects  of  stimulating  the  various  areas  refers  to  the 
brain  of  the  monkey. 

1  (On  the  superior  parietal  lobule).  Movement  of  the 
opposite  hind  foot  as  in  walking. 

2,  3,  4,  (The  fissure  of  Rolando).  Complex  movements  of 
the  opposite  leg  and  arm,  and  of  the  trunk,  as  in  swimming. 

a,  6,  c,  d,  (Postero-parietal  convolution).  Combined  move- 
ments of  the  fingers  and  wrist  of  the  opposite  hand,  closure 
of  the  fist,  and  prehensile  movements, 

5,  (Superior  frontal  convolution).  Extension  forward  of 
.the  opposite  arm. 

6;  (Upper  part  of  the  antero-parietal  convolution).  Sup- 
ination and  flexion  of  the  opposite  forearm. 

7,  (Median  portion  of  the  same  convolution).  Elevation 
of  the  opposite  angle  of  the  mouth — zygomatic  action. 

8,  (Lower  down  on  the  same  convolution).  Elevation  of 
the  ala  nasi  and  upper  lip,  and  depression  of  lower,  on  the 
opposite  side. 

9,  10,  (Inferior  extremity  of  the  same  convolution,  Broca's 
convolution).  Opening  of  the  mouth  with  (9)  protrusion 
and  (10)  retraction  of  the  tongue.  Region  of  aphasia.  Bi- 
lateral action. 

11,  (Between  (10)  and  postero-parietal  convolution).  Ac- 
tion of  jilatysma. 

12,  (Posterior  portions  of  superior  and  middle  frontal  con- 
volutions). Elevation  of  eyelids,  the  pupils  dilate,  and  the 
head  turns  toward  the  opposite  side. 


gf 


STRUCTURE  OF  THE  CEREBRUM. 


315 


i-d  of 


Sup- 


sroca  s 
irusion 
Bi- 

Ac- 

il  con- 
id  the 


13,  13',  (Supra-marginal  lobule  and  angular  gyrus).  The 
eyes  turn  to  the  opposite  side  with  an  upward  (13)  or  down- 
ward (13')  deviation.  The  pupils  generally  contracted, 
{Centre  of  vision.) 

14,  (Superior  temporo-spheuoidal  convolution).  Pricking 
of  the  opposite  ear,  the  head  turns  to  the  oppo  dte  side,  and 
the  puj)ils  are  dilated.     {Centre  of  heav'iny.) 

Fenier  places  the  centres  of  ta.ste  and  smell  at  the  ex- 
tremity of  the  temporo-sphenoidal  lobe,  and  that  of  touch 
in  the  gyrus  uneinatus  and  hippocampus  major. 

The  points  of  dilierencc  lietvveen  the  brain  of  man  and 
the  aj)eH,  and  tliose  of  all  other  animals,  consist  in  the  rudi- 
mentary character  of  the  olfactoiy  lobes,  the  well-duhned 
fissure  of  Sylvius,  the  larger  size  of  the  po>terior  lobe  com- 
pletely covering  the  cerebellum,  and  the  [)resence  of  poster- 
ior cornua  in  the  lateral  ventricles.  The  distinguishing 
features  between  the  brain  of  man,  and  the  ape,  consist 
of  the  larger  size  of  the  brain,  the  greater  number  and 
comphixity  of  the  convolutions,  and  the  blunted  quadran- 
gular contour  of  the  frontal  lobes  in  man  ;  and  the  greater 
prominence  of  the  temporo-sphenoidal  lobe,  the  distinctness 
of  the  parieto-occipital  fissure,  and  the  upward  oblique  di- 
rection of  the  fissure  of   Sylvius  in  the  ape. 

The  white  matter  of  the  cerebrum  consi'.ts  of  three 
kinds  of  tibres ;  diverging  or  peduncular,  transverse 
and  longitudinal  commissural  fibres.  The  diverging 
or  'peduncular  fibres  connect  the  cerebrum  with  the  me- 
dulla oblongata  and  spinal  cord,  and  constitute  the  crura 
cerebri.  Each  crus  consists  of  two  bundles,  super- 
ficial and  deep,  separated  by  a  dark  gray  mass  in  the 
interior — the  locus  niger.  The  superficial  fibres  are  con- 
tinued u]) wards  from  the  anterioT-  pyramids  to  the  cere- 
brum. The  deep  fibres  are  continued  upwards  from  the 
lateral  and  posterior  columns  of  the  medulla  and  the  olivary 
bodies.  As  the  peduncles  of  the  cerebrum  enter  the  hemi- 
spheres, they  diverge  from  one  another  to  enclose  the  inter- 
i8 


^ 


31G 


THE  NERVOUS  SYSTEM. 


c 

«). 

an 
I 

y 


"11:1  , 


peduncular  8j)ace,  and  the  fibres  of  each  pass  through  two 
large  masses  of  gray  matter,  the  ganglia  of  the  brain,  called 
the  thalami  optici  and  coipora  striata,  which  project  from 
the  upper  and  inner  side  of  each  peduncle.  Above  these 
masses  is  situated  the  great  transverse  commissure — the 
corpus  callosum — which  connects  the  hemispheres  together. 
The  space  bounded  by  the  ])oduncles  and  ganglia  on  the 
sides,  and  the  corpus  callosum  above,  forms  the  general  ven- 
tricular cavity.  The  upper  part  of  the  cavity  is  divided 
into  two  lateral  ventricles  by  the  .septum  lucidura,  and  the 
lower  part  constitutes  the  third  ventricle,  which  communi- 
cates above  with  the  lateral  ventricles,  and  behind  with  the 
fourth  ventricle,  through  the  itn^  a  tertio  ad  quartavi  ventri- 
culum.  The  Jifth  ventricle  is  situated  in  the  space  between 
the  two  layers  of  the  septum  lucidum.  The  transverse  fibres 
connect  together  the  two  hemispheres,  forming  the  corpus 
callosum,  and  the  anterior  and  posterior  commissures. 

The  longitudinal  fibres  connect  together  difierent  parts 
of  the  same  hemisphere.  They  form  the  fornix,  ttenia 
semicircularis,  peduncles  of  the  pineal  gland,  stria?  longi- 
tudinales,  gyrus  fomicatus,  and   the  fasciculus   uncinatus. 

Vascular  Supply. — The  blood-vessels  of  the  brain  are 
numerous  and  capacious,  it  being  supplied  by  four  large  ar- 
teries, the  two  internal  carotids  and  the  two  vertebral 
arteries.  These  vessels,  in  their  passage,  pursue  a  winding 
course  to  reach  the  brain,  the  object  of  which  is  to  increase 
the  extent  of  the  surface  over  which  the  blood  passes,  and 
thus  add  to  the  amount  of  impediment  produced  by  fric- 
tion, in  order  that  the  supply  may  be  more  equable  and 
uniform.  These  curvatures  in  the  vessels  also  tend  to 
moderate  the  force  with  which  the  blood  may  be  sent  to  the 
brain  under  certain  circumstances,  as  during  great  excite- 
ment, violent  exercise,  and  the  like.  These  vessels  also 
anastomose  freely  with  each  other  after  entering  the  crani- 
al cavity.  This  takes  place  not  only  between  the  smaller 
branches,  but  also  between  the  primary  trunks ;  the  former 


FUNCTION  OF  THE  CEREBRUM. 


317 


ugh  two 
n,  called 
ect  from 
ve  these 
ire — the 
together. 
,  on  the 
oral  ven- 
1  divided 
and  the 
ammuni- 
with  the 
71  ventri- 
between 
7'se  fibres 
le  corpus 
es. 

3nt  parts 
X,  tsenia 
IB  longi- 
ncinatus. 
rain  are 
large  ar- 
ertebral 
winding 
increase 
ises,  and 
by  fric- 
able  and 
tend  to 
nt  to  the 
,t  excite- 
:s  also 
e  crani- 
smaller 
former 


is  seen  all  over  the  surface  of  the  encephalon  ;  the  latter 
constitutes  the  well-known  circle  of  Willis.  This  is  form- 
ed in  front  by  the  anterior  communicating  and  anterior 
cerebral  arteries ;  on  each  side,  by  the  trunk  of  the  internal 
carotid  and  the  jwsterior  communicating ;  and  behind  by 
the  posterior  cerebral  and  point  of  the  basilar.  These  ves- 
sels divide  and  subdivide  upon  the  suiface  of  the  brain, 
until  they  terminate  in  very  small  arteiios,  which  aie  con- 
nected together  by  some  areolar  tissue,  constituting  the  pia 
mater,  from  which  very  small  vessels  are  given  off"  that 
l)ierce  the  brain  substance.  No  large  vessels  pierce  the 
cerebral  substance,  except  at  the  perforated  spaces ;  but 
prolongations  of  the  pia  matter,  carrying  with  them  the 
blood  vessels,  pass  into  the  interior  of  the  brain  at  the  tran- 
verse  fissure,  to  form  the  velum  interpositum  and  choroid 
plexuses  which  arc  situated  in  the  ventricles. 

Function  of  the  Cerebrum. — From  its  anatomical  re- 
lation, the  brain  does  not  appear  to  be  one  of  the  essen- 
tial or  fundamental  poitions  of  the  nervous  system,  but  is  a 
superadded  organ,  receiving  all  its  impulses  to  action  from 
the  parts  below,  and  acting  upon  the  body  at  large  through 
them.  But  its  great  size,  its  position  at  the  summit  of  the 
cerebro-spinal  system,  and  the  vesicular  substance  of  its 
convolutions  affording  a  termination  to  the  fibres  in  connec- 
tion with  it,  mark  it  out  as  the  highest  in  its  functional  re- 
lations, and  as  the  organ  through  which  all  the  processes  of 
thought,  reason,  and  intelligence  are  carried  on.  It  is  the 
organ  of  intellectual  action,  emotion,  ideo-motor  action  and 
volition,  the  seat  of  which  is  the  gray  matter  of  the  convo- 
lutions. 

There  is  a  very  close  correspondence  between  the  relative 
development  of  the  cerebrum,  in  the  several  tribes  of  verte- 
brata,  and  the  degree  of  intelligence  they  respectively  pos- 
sess. In  the  lower  animals  it  is  difficult  to  say  what  part 
of  their  actions  may  be  regarded  as  instinctive  and  what  as 
intelligent.     Intelligent  actions  are  exhibited  :   1st,  in  the 


318 


THE  NERVOUS  SYSTEM. 


c 
c 

t 

L 

^ 

■I 
•A 

IM 
I 

f 

til 

t 

M 


variety  of  means  used  to  accomplish  tlic  same  enfl.s  by  dif- 
ferent individuals,  and  by  the  same  individual  at  diffbient 
times  ;  2nd,  in  the  improvemen!;  in  the  mode  of  accomplish- 
ing the  object,  which  results  from  experience;  .'hd,  in  the 
adaptation  of  means  to  altered  circumstances.  The  difi'ei*- 
ence  between  the  intelligence  of  lower  aninmls  and  pure  in- 
stinct, is  well  seen  in  comparing  birds  with  insects.  Their 
instinctive  propensities  are  nearly  similar ;  but  in  the  ad- 
aptation (jf  their  operations  to  peculiar  circumstances,  birds 
display  a  ceitain  degree  of  intelligence.  Certain  tribes  of 
birds,  especially  the  parrot  and  its  allies,  are  capable  of  be- 
ing taught  to  perform  tricks  and  to  pronounce  words,  in 
which  they  exhil)itsim[)le  actsof  reasoning,  similar  to  those 
of  a  child  when  first  learning  to  talk.  Some  of  the  domes- 
tic animals,  as  tlie  dog  and  the  hoise,  manifest  a  consider- 
able degree  of  intelligence.  There  is  no  evidence,  however, 
that  any  of  the  lower  animals  have  the  power  of  directing 
their  mental  operations  in  obedience  to  the  will. 

With  reference  to  the  sensibility  of  cerebral  matter,  it  has 
been  ascertained  by  experiment  that  no  sensation  of 
pain  is  produced  by  irritation  of  the  vesicular  or  fibrous 
substance.  In  fracture  of  the  skull,  accompanied  by  pro- 
trusion of  the  cerebral  matter,  it  may  be  excised  without 
exciting  either  sensation  or  convulsive  motion.  When  one 
of  the  hemispheres  is  removed  from  an  animal,  it  is  follow- 
ed V)y  temporary  weakness  of  the  limbs  on  the  opposite  side 
of  the  body,  and  a  loss  of  sight  in  the  opposite  eye,  but  the 
pupil  remains  active.  When  both  hemispheres  are  remov- 
ed from  a  j)igeon,  the  animal  remains  motionless  and,  ap- 
pears to  be  in  a  sleepy  state,  from  which  it  cannot  be  fully 
aroused,  but  consciousness  still  remain-:!,  the  persistence  of 
which  proves  that  the  cerebrum  is  not  its  exclusive  seat. 
In  the  frog  removal  of  the  cerebrum  is  attended  with  simi- 
lar results.  The  animal  remains  motionless  unless  when 
disturbed.  It  sits  up  naturally  and  breathes  quietly ;  but 
when  pricked  it  jumps  away,  or  thrown  into  the  water  it 


FUNCTION  OF  THE  CEREBRUM. 


319 


by  aii- 
Hff'eront 
iinj)lish- 
,  in  tho 
e  difi'or- 
|)ure  in- 
Their 

tliu  atl- 
es,  binls 
tribes  of 
e  of  be- 
rords,  ill 
to  those 
3  domes- 
lonsider- 
lowever, 
lirecting 

jr,  it  has 
tion    of 

fibrous 

by  pro- 

witbout 

len  one 

foUow- 

Isito  bide 

but  the 

lemov- 
irid,  ap- 

e  fully 

ence  of 
|ve  seat. 

h  simi- 
when 

y;  but 

ater  it 


swiuis.  In  this  state  a  reptile  or  bird  may  survive  many 
weeks  if  its  physieal  wants  bo  supplied.  The  influence  of 
disease  on  the  cerebrum  is  somewhat  anomalous.  In  some 
instances  extensive  disease  has  occurred  in  one  hemisphere, 
without  any  obvious  injury  to  the  mental  powers,  or  inter- 
ruption of  the  influence  of  the  mind  on  tho  body  ;  Vjut  mor- 
bid phenomena  are  invariably  i)rcsent  when  both 
hemispheres  are  att'ected.  On  the  other  hand  a  .sudden 
lesion,  although  of  a  trifling  character,  may  occasion  very 
severe  symptoms;  for  example,  a  slight  eft'usion  of  blood  in 
or  around  the  substance  of  the  corpus  striatum  is  followed 
by  paralysis  and  loss  of  sensation  in  the  opposite  side  of  the 
body.  Although  there  are  two  hemispheres,  and  each  ap- 
])ears  capable  of  discharging  in  a  general  way  the  functions 
of  both,  yet  the  mind  combines  the  impressions  derived 
from  both,  and  the  ideas  or  impiessions  become  single. 
The  theory  is  steadily  gaining  ground  that  each  faculty  of 
the  mind  has  a  special  portion  of  the  brain  appropriated  to 
it,  just  as  other  com})ound  organs  or  sj'Stems  in  the  body, 
in  wliich  each  has  its  special  function.  This  is  supported 
by  the  difference  in  the  mental  functions  in  different  indi- 
viduals, and  at  different  periods  of  life ;  also  by  the  phe- 
nomena of  some  forms  of  "  ^ sanity.  In  the  latter  it  is  not 
often  that  all  the  faculties  are  disordered ;  some  are  increas- 
ed while  others  are  diminished.  The  phenomena  of  dreams, 
in  which  some  of  the  faculties  appear  to  be  awake,  while 
others  are  at  rest,  also  support  this  view  to  some  extent.  In 
cases  of  hemiplegia,  in  which  the  posterior  part  of  the 
third  frontal  convolution  of  the  left  side  is  diseased,  it  is 
frequently  associated  with  ajyha/iia  or  loss  of  power  of  ex- 
pressing ideas  in  language.  It  has  therefore  been  inferred 
that  this  portion  of  the  brain  is  the  centre  for  language, 
or  rather  that  its  healthy  condition  is  essential  to  the 
faculty  of  speech.  The  empirical  method  by  which  Gall 
first  fixed  upon  certain  parts  of  the  brain  as  the  seat  of  cer- 
tain faculties,  is  exposed  to  the  serious  fallacy  that  a  part 


320 


THE  NERVOUS  SYSTEM. 


c 
c 

c 

L 


am 
I 

>** 
I 


on  the  surface  of  the  brain  may  appear  largely  developed 
in  consequence  of  the  large  size  of  some  subjacent  or  neigh- 
boring part, — for  example,  a  thick  neck  and  large  occipital 
region  may  indicate  a  large  pons  and  medulla  more  fre- 
quently than  a  large  cerebellum.  Again,  with  respect  to 
the  cranium  itself,  large  prominences  just  above  the  eye- 
brows may  indicate  large  frontal  sinuses  rather  tiian  a  large 
development  of  "  certain  organs  "  on  the  anterior  lobes  of 
the  cerebrum.  Gall  divided  the  whole  cerebrum  into 
twenty-seven  dift'eront  organs  to  represent  different  facul- 
ties, and  Spurzheim  divided  it  into  thirty-five.  In  some 
diseases,  as  for  example,  in  typoid  fever,  the  mind  is  more 
or  lessobtunded,and unable tocombine  the  impressions  receiv- 
ed through  both  hemispheres,  and  the  patient  fancies  him- 
self as  two  individuals.  He  also  sometimes  holds  converse 
with  the  alter  ego  he  fancies  is  lying  alongside  of  him  and 
constitutes  a  part  of  himself,  or  requests  some  attention  to 
be  given  to  the  person  beside  him,  when  in  reality  the  at- 
tentions are  required  for  himself. 

The  capacity  for  performing  mental  acts  is  known  as  the 
intellect,  or  reasoning  power ;  and  the  capacities  for  those 
various  forms  of  intellectual  activity  which  pertain  to  the 
mind  are  called  the  intellectual  faculties.  These  are  per- 
ception, imagination,  memory  and  judgment.  When 
impressions  are  made  upon  some  part  of  the  body  that  is 
supplied  with  afferent  nerves,  they  are  transmitted  through 
them  to  the  sensorium,  and  occasion  affections  of  the  con- 
sciousness, which  are  called  sensations'  Every  impression 
which  affects  the  consciousness  produces  some  change  in 
the  nervous  centre,  by  which  that  impression  is  perpetuated 
in  such  a  manner  as  to  permit  of  its  being  again  called  up 
before  the  mind  at  any  future  time.  The  nature  of  the 
change  by  which  sensory  impressions  are  thus  registered  is 
not  understood,  and  probably  never  will  be.  The  acuteness 
with  which  particular  sensations  are  felt,  depends  on  the 
degree    of    attention   they    receive    from   the   mind  ;    for 


FUNCTION  OF  THE  CEREBRUM. 


321 


?veloped 
>r  neigh- 
occipital 
iiore  fre- 
specfc  to 
the  eye- 
ri  a  large 
lobes  of 
urn  into 
nt  facul- 
In  some 
is  more 
IS  receiv- 
;ies  him- 
converse 
him  and 
ention  to 
y  the  at- 

m  as  the 
or  those 

to  the 
are  'per- 

When 

that  is 
through 
;he  con- 
press  ion 
tange  in 
aetuated 
ailed  up 

of  the 
stei'ed  is 
cuteness 

on  the 
ad  ;    for 


example,  ordinary  impressions  are  not  felt  during  sleep,  or 
when  the  mind  is  engaged  in  some  deep  subject  of  study. 
On  the  other  hand,  impressions  which  are  in  themselves 
very  slight  may  produce  painful  sensations,  when  the  mind 
is  directed  strongly  towards  them.  They  are  also  much 
modified  by  the  influence  of  habit.  Sensations  not  attended 
to  bec(jme  blunted  by  frequent  repetition ;  whilst  sensations 
attended  to  become  much  more  readily  cognizable  by  the 
mind.  Every  student  knows  that  the  efliuvia  of  the 
dissecting  room  becomes  tolerable,  after  the  nose  has  become 
habituated  to  it. 

In  some  instances,  sensations  may  be  produced  by  in- 
ternal causes  ;  these  are  called  subjective  sensations,  in 
contradistinction  to  objective,  which  are  caused  by  a  real 
material  object.  The  most  common  cause  of  these  sub- 
jective sensations  is  congestion  or  inflammation ;  e.  g.,  con- 
gestion in  the  nerves  of  common  sensation  gives  rise  to 
pain  or  uneasiness  ;  in  the  retina  or  optic  nerve,  it  produces 
"  flashes  of  light ;  "  and  in  the  auditory  nerve  it  occasions 
"a  noise  in  the  ears."  Again,  subjective  sensations  may 
be  produced  by  sensations  originating  in  objective  impres- 
sions on  other  parts,  as  e.  g.,  a  calculus  in  the  bladder  gives 
rise  to  pain  in  the  glans  penis ;  disease  of  the  hip  occasions 
pain  in  the  knee. 

The  mental  recognition  of  the  cause  of  sensation  is  called 
perception.  For  the  production  of  a  sensation  a  conscious 
state  of  the  mind  is  all  that  is  required ;  but  for  the 
exercise  of  the  perceptive  power,  the  mind  must  be  directed 
towards  the  sensation,  and  hence,  when  the  mind  is  inactive, 
or  engaged  in  study,  the  sensation  may  not  be  perceived 
or  remembered.  The  perception  of  sensation  gives  rise  to 
ideas;  some  of  these  partake  of  the  nature  of  feeling ; 
others  relate  to  knowledge.  An  idea  is  a  mental  rej)resenta- 
tion  of  an  object  which  has  been  perceived  by  the  mind— ^ 
something  grasped  by  the  mind,  and  held  up  before  it  is  an 
intelligible  object  of  contemplation.     Ideas  may  be  com- 


322 


THE  NERVOUS  SYSTEM. 


c 
t 

Mm 


•V 
m. 

t 

c 

ft* 

Ifc' 

II 

ei 

%i 

I' 
'•"(> 
inr. 

Hi.. 

(» 


raunicated  and  rendered  intelligible  to  other  minds  by 
means  of  visible  signs,  or  by  spoken  language,  in  w^'^h 
certain  combinations  of  sounds  are  used  to  express  ideas  ; 
and  the  nearer  the  signs  or  sounds  employed  are  to  the 
natural  expressions  of  the  ideas  which  the}'^  represent,  the 
more  readily  are  they  comprehended. 

When  ideas  are  associated  with  feelings  of  pain  or 
pleasure,  they  give  rise  to  emotions.  These,  unlike  ideas, 
cannot  be  communicated  or  expressed  in  language  to  others; 
they  are  unutterable.  Those  emotional  states  of  the  mind 
which  determine  a  great  part  of  the  conduct  of  individuals, 
are  the  result  of  the  attachment  of  the  feelings  of  pleasure 
and  pain,  and  of  other  forms  of  emotional  sensibility  to 
certain  classes  of  ideas.  Thus,  grief  is  the  painful  con- 
templation of  loss,  misfortune,  or  evils  of  any  kind.  Jo^/  is 
the  pleasurable  feeling  which  accompanies  success,  good 
fortune,  or  good  jnospects,  etc.  Fear  is  a  painful  emotion 
excited  by  an  expectation  of  future  evil.  Hope  is  the 
pleasurable  exnectation  of  future  enjoyment.  Benevolence 
is  the  pleasurable  contemplation  of  doing  good  to  others. 
Malevolence  is  a  positive  pleasure  in  the  contemplation  of 
the  misfortunes  of  others,  and  so  on.  The  emotions  are 
partly  under  the  control  of  the  will,  and  partly  independent 
of  it. 

The  determining  power  of  the  ivill  acts  both  upon  the 
body  and  the  mind  ;  but  the  only  sensible  effect  which  the 
strongest  effort  of  volition  can  produce  on  the  bodily  frame 
is  that  of  contraction  of  the  voluntary  muscles.  The  im- 
mediate oiieration  of  the  will  is  not  upon  the  muscles,  but 
upon  the  biuin,  in  which  it  excites  nerve  force,  which  is 
transmitted  along  the  nerves,  and  stimulates  the  muscular 
tissue  to  contraction.  With  reference  to  the  action  of  the 
will  upon  the  mind,  it  may  be  said  that  it  possesses  the 
power  of  recalling  ideas  which  are  present  in  the  mind,  ex- 
cluding some  and  bringing  others  more  prominently  before 
it.      This  is  effected  by  the  power  of  voluntary  attention. 


CORPORA  QUADRIGEMINA. 


323 


nds   by 

1  ideas  ; 

to  the 

ent,  the 

pain  or 
e  ideas, 
)  others; 
lie  mind 
viducils, 
pleasure 
)ility  to 
ful  ecn- 

Joy  is 
5S,  good 
emotion 

is  the 
evolence 

others, 
itiou  of 
ons  are 
wndent 

Don  the 

ich  the 

y^  frame 

he  im- 

es,  but 

lieh   is 

uscular 

of  the 

es  the 

nd,  ex- 

before 

ention, 


which  is  the  chief  means  through  which  the  sequence  of  our 
thoughts  is  directed  by  tiie  will.  When  the  will  is  most 
strongly  exerted,  it  causes  the  consciousness  to  be  so  com- 
pletely engaged  by  one  train  of  ideas  that  the  mind  is,  for 
the  time,  incapable  of  receiving  any  other  idea  or  impression, 
the  individual  being  as  insensible  as  if  he  were  in  a  pro- 
found sleep.  This  power  of  concentration  of  the  mind  on 
the  subject  of  study,  is  of  very  great  importance  and  ad- 
vantage in  the  acquirement  of  knowledge  and  the  pursuit  of 
truth,  and  one  which  is  capable  of  cultivation  to  a  consider- 
able extent  by  habitual  exercise.  Sometimes  the  cerebral 
processes  are  carried  on  unconsciously,  as  for  example,  when 
one  has  tried  in  vain  to  remember  some  particular  date,  oc- 
.  urrence  or  name,  and  has  given  it  up,  and  hours  or  days 
afterwards,  it  suddenly  and  unexpectedly  flashes  across  the 
mind.     This  is  called  unconscious  cerebration. 

The  crura  cerebri  are  the  principal  conductors  of  impres- 
sions to  and  from  the  cerebrum.  When  one  of  them  is 
divided,  the  animal  moves  round  and  round  on  a  vertical 
axis  from  the  injured  to  the  sound  side  ;  this  is  caused  by  a 
partial  paralysis  on  the  side  opposite  the  injury.  In  each 
crus  cerebri  is  found  a  small  mass  of  gray  substance,  the 
locus  niger,  from  which  arises  the  third  cranial  nerves,  so 
that  this  may  be  looked  upon  as  the  nervous  centre  for  the 
chief  movements  of  the  eyeballs. 

The  corpora  quadrigemina,  including  the  corpora  genicu- 
lata  are  the  representatives  of  the  optic  lobes  in  birds, 
reptiles  and  fishes,  and  may  be  considered  as  centres  of  the 
sense  of  sight,  since  their  removal  or  diseased  condition  is 
accompanied  with  blindness.  Injury  or  disease  on  one  side 
is  followed  by  blindness  of  the  opposite  eye,  and  a  slight 
rotatory  motion,  as  after  the  division  of  the  crus  cerebri ;  the 
pupil  is  also  dilated.  They  are  not  only  the  centres  from 
which  the  optic  nerves  arise  in  part,  but  also  the  organs 
through  which  the  mind  perceives  the  sensation  of  light 
The  centres  for  co-ordination  of  the  movements  of  the  eye- 


324. 


THE  NERVOUS  SYSTEM. 


c 
t 

m 
I 

I 


balls,  and  contraction  of  the  pupil,  lie  in  the  nates  or  anterior 
tubercles  of  the  corpora  quadrigemina. 

The  thalami  optici  are  also  concerned  to  a  certain  extent 
in  the  function  of  vision,  for  part  of  the  fibres  of  the  optic 
tracts  may  be  traced  to  their  surfaces.  In  persons  born 
blind,  the  optic  thalami,  and  also  the  corpora  quadrigemina, 
are  found  extremely  small.  Destruction  of  one  of  them  pro- 
duces effects  similar  to  those  of  division  of  the  crus  cerebri ; 
the  animal  remains  standing,  and  turns  continually  round. 

The  corpora  striata  were  supposed  by  Magendie  to  be  the 
centres  of  motor  power  for  ^ac/ayanZ  moverat.o,  and  that 
foTivarcl  movement  was  excited  by  the  cerebellum,  these 
two  powers  being  exactly  counterbalanced,  and  hence  divi- 
sion of  the  corpora  striata  caused  an  irresistible  tendency 
to  run  forwards.  This,  however,  has  not  been  confirmed  by 
other  exjierimenters.  Longet  and  others  assert  that  animals 
remain  stupid  and  immovable  after  division  of  the  corpora 
striata,  and  it  is  only  when  irritated  by  pinching  or  pricking 
that  they  exhibit  any  disposition  to  move.  Lesion  of  both 
thecorpora  striata  and  optic  thalami  on  one  side  of  the  human 
brain,  is  attended  with  loss  of  sensation  and  voluntary  power 
on  the  opposite  side  of  the  body  and  face.  The  corpora 
striata  are  regarded  by  some  as  motor,  and  the  optic  thalami 
as  sensory  ganglia,  but  this  division  of  functions  has  not  yet 
been  clearly  proved. 

The  corpus  callosu7)i  connects  together  the  two  hemi- 
spheres of  the  cerebrum.  It  is  entirely  absent  in  birds, 
reptiles  and  fishes.  Its  division  is  followed  by  severe 
general  injury.  It  probably  enables  the  two  sides  of  the 
brain  to  act  in  harmony  in  the  performance  of  its  highest 
functions. 

The  Mind  and  its  Relation  to  the  Body. — With  lefer- 
ence  to  the  relation  of  mind  and  matter,  and  the  nature 
and  source  of  mental  phenomena,  there  are  two  theories, 
that  of  the  materialist  and  the  spirit italist.  The  material- 
ist  supposes  that  all  the  operations  of  the  mind  are  but 


sen 


MIND  IN  RELATION  TO  THE  BODY. 


325 


hemi- 

birds, 

severe 

of  the 


"  expre.sions  of  material  changes  in  the  brain ;"  that  thus 
man  is  but  a  thinking  machine,  his  whole  conduct  being 
determined  by  his  original  constitution,  his  character  being 
formed  for  him  and  not  hy  him,  his  actions  being  simply 
the  result  of  the  reaction  of  his  cerebrum  upon  the  impres- 
sions which  called  it  into  play.  According  to  this  doctrine, 
the  highest  elevation  of  man's  'psychical  nature  is  to  be  at- 
tained by  proper  attention  to  those  circumstances  which 
promote  his  physical  development.  The  arguments  in  sup- 
port of  this  theory  are  : — 1st,  the  dependence  of  the  normal 
activity  of  the  mind  upon  the  healthy  nutrition  of  the 
brain,  and  its  proper  supply  of  pure  blood  ;  2nd,  the  pecul- 
iar effects  of  lesions  of  the  brain  upon  the  intellectual  oper- 
ations, as  is  seen  in  loss  of  speech,  memory,  etc.,  after  severe 
injury  to  the  head;  3rd,  the  production  of  mental  imbecility 
as  a  result  of  disease  in  the  parents,  or  defective  nutrition 
in  the  offspring  during  childhood  ;  and — 4th,  the  complete 
perversion  of  the  mind  and  moral  feelings  which  is  pro- 
duced by  intoxicating  agents.  Now,  though  this  doctrine 
recognizes  some  great  facts  regarding  the  dependence  of 
mental  operations  upon  the  organization  and  functional 
activity  of  the  nervous  system,  yet  there  is  beyond  and 
above  all  this  a  self-determining  power  which  can  rise 
above  the  promptings  of  external  suggestions,  and  which 
can  suit  external  circumstances  to  its  own  requirements,  in- 
stead of  being  completely  subjugated  by  them. 

The  spiritualist  regards  the  mind  in  the  light  of  a  separ- 
ate immaterial  existence  connected  with  the  body,  but  not 
in  any  way  dependent  upon  it,  except  as  deriving  its  know- 
ledge of  external  things  through  its  agenc}',  and  as  making 
use  of  it  to  execute  its  determination  so  far  as  these  relate 
to  material  objects.  According  to  this  theory,  the  operations 
of  the  mind,  having  no  relation  to  those  of  the  body,  are 
never  affected  by  its  irregularities  or  defects  of  functional 
activity  ;  and  the  mind,  thus  independent  of  the  body,  is 
endowed  with  a  complete  power  of  self-goveiiinient,  and  is 


326 


THE  NERVOUS  SYSTEM. 


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F 


ott. 


responsible  for  all  its  actions.  But  nothing  can  be  more 
plain  than  that  the  introduction  of  intoxicating  agents  into 
the  system  really  perverts  the  action  of  the  mind,  and  oc- 
casions many  strange  results  at  variance  with  its  normal 
action.  So  that,  however  true  it  may  be  that  there  is  some- 
thing in  our  mental  constitution  beyond  and  above  any 
agency  which  can  be  attributed  to  matter,  the  operations  of 
the  mind  are  in  a  great  degree  determined  by  the  material 
conditions  with  which  they  are  so  intimately  associated. 
The  whole  system  of  education  recognizes  the  importance 
of  external  influences  in  the  formation  of  the  character ; 
and  it  is  the  duty  of  every  teacher  to  foster  the  develop- 
ment and  promote  the  right  exercise  of  that  power  by  which 
each  individual  becomes  the  director  of  his  own  conduct. 

Hence  it  will  be  seen  th.it  any  attempt  to  bring  mind  and 
matter  into  the  same  category  is  attended  with  ditticulty, 
since  no  relation  of  identity  can  exist  between  them.  But 
although  no  relation  of  identity  or  analogy  subsists  between 
mind  and  matter,  a  very  close  relation  may  be  shown  to 
exist  between  iniind  and  fores,  or  between  mind-force  and 
nerve-force.  In  the  phenomena  of  voluntary  movements 
the  will  operates  upon  the  nervous  matter,  and  developes 
nerve-force,  the  transmission  of  which  along  the  nerve 
trunks  is  the  determining  cau.se  of  muscular  contraction. 
Hero  is  evidence  of  the  excitement  of  nerve-force  by  mental 
agency.  The  converse  of  this  is  equally  true,  viz.,  that 
mental  activity  may  be  excited  by  nerve-force.  This  is  the 
case  in  every  act  in  which  the  mind  is  excited  through  the 
instrumentality  of  the  sensorium  ;  the  impression  is  first 
conveyed  to  the  sensorium  (or  sensory  ganglia),  in  which  it 
produces  a  certain  active  condition  of  the  nervous  matter, 
which  is  the  immediate  antecedent  of  all  consciousness — 
whether  of  emotions  or  ideas.  And  since  the  will  can  de- 
velope  nerve- force,  and  as  nerve-force  can  develope  mental 
activity,  there  must  be  a  correlation  between  the  two  forces, 
not  less  intimate  than  that  which  exists  between  nerve-force 


INFLUENCE  OF  MIND  ON  THE  BODY. 


327 


and  electricity.  The  nervous  matter  of  the  cerebrum  is  the 
material  substratum  through  which  the  metamorphosis  of 
nerve-force  iuto  mind-force,  and  mind-force  into  nerve-force 
is  effected,  and  like  all  other  changes,  every  act  of  the  mind 
involves  the  disintegration  of  the  nervous  substance  which 
ministers  to  it. 

The  influence  of  the  mind  over  the  body  is  a  most  re- 
markable phenomenon,  and  one  well  worthy  of  attention. 
Many  of  its  effects  are  quite  familiar  ;  for  example,  fear  or 
great  anxiety  of  mind  produces  a  desire  for  frequent  mictu- 
rition, and  not  unfrequently  the  bowels  are  moved  also. 
The  announcement  to  the  patient  of  the  arrival  of  the  ac- 
couclieur,  suspends  for  a  time  the  labor  jiains  The  sight, 
or  even  the  thought  of  very  unj)alatable  medicine,  produces 
nausea,  and  sometimes  vomiting.  Under  the  influence  of 
the  mind,  opium  pills  have  been  known  to  produce  cathar- 
sis, when  the  patient  su|)posed  that  he  had  taken  a  cathar- 
tic. In  this  way  also,  persons  have  been  much  benefited, 
and  in  some  instances  entirely  cured,  by  the  simplest  reme- 
dies. Much  of  the  success  of  the  homoiopathist  is  no  doubt 
due  to  this  fact.  In  all  modes  of  treatment,  therefore,  it  is 
absolutely  necessary  to  have  the  entire  confidence  of  the 
patient.  It  has  also  been  observed,  that  when  the  mind  is 
directed  to  any  tumor  or  growth  of  the  body,  its  increase  is 
greatly  accelerated. 

In  consequence  of  the  waste  of  nerve  tissue  during  its 
activity,  it  is  necessary  that  a  periodical  suspension  should 
take  place  in  order  to  permit  of  nutritive  regeneration;  this 
is  called  sleep.  In  deep  sleep  there  is  a  state  of  complete 
unconsciousness,  and  the  body  may  remain  for  a  considera- 
ble time  motionless  ;  but  the  individual  is  capable  of  being- 
aroused  by  external  impressions.  In  this  it  differs  from 
coma,  which  is  generally  the  result  of  some  pressure  upon 
the  brain,  in  which  the  patient  is  incapable  of  being  aroused. 
The  tendency  to  fall  asleep  is  favored  by  a  succession  of 
dull,  monotonous  sounds,  as  a  dull,  prosy  speech  or  sermon  ; 


328 


THE  NERVOUS  SYSTEM. 


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or  by  aound.s  accompanied  by  gentle  movi'inonts,  as  is  seen 
in  putting  infants  asleep.  Anotiier  method  is  to  close  the  eyes 
and  lix  the  attention  upon  some  object,  or  refteat  a  certain 
word  until  the  mind  becomes  completely  lost  or  unconscious. 
The  average  amount  of  sleep  required  by  a  healthy  adult 
is  about  eight  hours  in  twenty-four  ;  children  require  more. 
On  some  occasions  the  sleep  is  more  or  less  distur])ed  by 
dreams.  These  generally  refer  to  something  that  has  en- 
gaged the  attention  previously  ;  but  in  some  instances  they 
would  appear  to  indicate  things  that  are  to  happen  ;  at  all 
events,  there  is  in  many  instances  a  singular  coincidence 
between  dreams  and  occin-rences  which  follow  them.  An 
uneasy  or  anxious  state  of  mind  is  unfavorable  to  sleep.  It 
is  said  that  criminals  under  sentence  of  death  sleep  badly 
while  they  have  hopes  of  a  reprieve,  but  as  soon  as  they  are 
assured  that  their  death  is  inevitable,  they  usually  sleep 
more  soundly. 

Derangement  of  the  digestive  organs,  or  a  disturbed  state 
of  mind,  in  some  instances,  gives  rise  to  a  dreaming  state 
called  somnambnlisni.  In  this  state  the  individual  acts  as 
if  he  were  awake,  and  as  if  all  the  phenomena  presented  to 
him  were  real.  He  answers  questions  rationally  and  with 
readiness ;  he  walks  with  precision  and  avoids  obstacles ; 
yet,  not  unfrequcntly,  accidents  happen  which  show  that  he 
has  not  full  command  of  his  senses. 

A  state  remarkably  analogous  to  somnambulism  may  be 
induced  in  some  persons,  which  has  been  called  mesmerism. 
The  production  of  this  state  requires  the  apparent  influence 
of  another  individual,  who  looks  directly  in  the  face  of  the 
pei'son  experimented  upon,  and  makes  certain  movements 
before  him  called  2^(-^sses ;  or  the  person  is  required  to  gaze 
steadfastly  upon  a  piece  of  metal  or  other  substance  held  in 

J  hand,  until  a  state  of  unconsciousness  is  induced.  Re- 
markable statements  have  been  made,  implying  that  in 
these  cases  the  faculties  are  very  much  exalted,  and  the 
peri,.n  acquires  powers  of  a  superhuman  kind.    Such  state- 


CRANIAL  NERVES. 


329 


ments,  however,  are  made  by  those  interested  in  such 
seances,  or  by  those  who  are  ignorant  of  the  deception  re- 
sorted to  in  order  to  obtain  notoi'iety. 


ited  to 

with 

iiacles ; 

lat  he 

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iuence 
of  the 
enients 
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held  in 
Re- 
hat  in 
nd  the 
state- 


CRANIAL   NERVES. 

The  cranial  nerves  include  those  nerves  which  arise  from 
some  part  of  the  cerebro-spiiial  contrc  and  are  transmitted 
through  foramina  at  the  base  of  the  brain.  There  are  in 
reality  tw(;lve  pairs  of  cranial  nerves,  but  they  are  ar- 
ranged in  nine  pairs  in  the  following  order  from  before  back- 
wards : — 


1st     Olfactory 

2nd   Optic 

Motor  Oculi 
Pathetic 


3rd 
4th 
5th 
6th 


^,,    f  Facial  or  portio  dura 

(  Auditory  or  portio  mollis 
C  Glosso-pharyngeal 

8th  <  Pnoumofifastric 


Trifacial  or  trigemini      i.  Spinal  accessory, 


Abducens 


9th     Hypoglossal. 


The  nerves  of  the  7th  and  8th  pairs  are  so  combined  in 
their  distribution,  that  it  is  almost  impossible  to  separate 
them  in  either  their  anatomy  or  physiology.  The  cranial 
nerves  may  be  subdivided  into  four  groups,  according  to  the 
peculiar  function  of  each,  viz.,  1st,  nerves  of  special  sense, 
as  the  olfactory,  optic,  auditory,  the  lingual  branch  of  the 
trifacial,  and  part  of  the  glosso-pharyngeal ;  2nd,  nerves  oj 
common  sensation,  as  the  greater  portion  of  the  fifth,  and 
part  of  the  glosso-pharyngeal ;  3rd,  nerves  of  motion,  as 
the  motor  oculi,  pathetic,  part  of  the  trifacial,  abducens, 
facial,  and  hypoglossal;  and  4!th,  mixed  nerves,  as  the 
pneumogastric  and  spinal  accessory. 

The  olfactory  nerve  arises  from  the  cerebrum  by  three 
roots,  and  presents  a  bulbous  enlargement  which  rests  upon 
the  cribriform  plate  of  the  ethmoid  bone,  from  which  delicate 
filaments  are  given  off  which  supply  the  nose.  It  is  the 
nerve  of  the  special  sense  of  smell.     In  structure  it  differs 


:{:{() 


THE  NERVOUS  SYSTEM. 


from  tlio  other  iiervoH,  in  boiii^  soft  and  grayisli  in  color, 
and  tlcstituto  of  tlie  whito  substance  of  Schwann. 

Kljf.    1 10, 


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s; 

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Ol. 


Kxtonial  wall  of  tlio  110*0.  a,  01fttotor.v  nerve  ;  h,  olfiictory  bulb  upon  the 
eribriionn  pliile  of  thoi'lliinoid  ;  Iil'Iow  i.s.sut^ji  lliu  Uiatiibutioii  of  the  branches 
uiHiii  the  iiji|)i>r  and  tlin  niiihlle  tiirbiiia  od  bone»  ;  c,  fifth  !n:vve  \»;»h  Ous- 
veriun  u>ini;lioii  ;  o,  its  palatine  bnincheb. 

Tlie  ('/>//<;  nerve  is  distributed  to  tl.e  eye,  in  which  it  ex- 
pands to  form  the  internal  layer  of  the  retina,  and  is  tlie 
nt^'ve  of  the  special  sense  of  sight.  Division  of  the  optic 
nerve  produces  total  blindness  and  dilatation  of  the  pupil, 
but  does  not  destroy  ordinary  sensibility  or  paralyze  mus- 
cular action. 

The  auditory  no've  (vortio  mollis)  is  the  s])ecial  nerve  of 
the  sense  of  hearing.  It  convevs  to  the  brain  the  sensation 
of  sound,  and  is  incapable  of  transuiitting  any  other,  being 
entirel}'  destitute  of  ordinary  sensibility.  Tlie  filarnents  Sive 
distributed  to  the  cochlea,  semicircular  canals  and  vestibule. 

The  motor-ocidl  is  a  nerve  of  motion,  and  is  distributed 
to  all  the  muscles  of  the  eyeball,  except  the  superior  ob- 
lique and  external  rectus.  It  also  supplies  motor  filaments 
to  the  circular  fibres  of  the  iris.  In  paralysis  of  this 
nerve,  the  up})er  eyelid  falls  down  over  the  eye,  so  that  it 
appears  half  closed  {ptosis),  the  pupil  is  dilated  and  insens- 


TRIFACIAL  NERVE. 


331 


ible  to  light,  tho  movements  of  the  oyisball  arc  nearly  sus- 
pended, and  the  eye  is  directed  outwards,  <)vvin«(  to  tho 
action  of  the  external  rectus.  OwiuLjto  the  irre<;ularity  of 
the  axes  of  the  eyes,  double  sight  is  often  experienced.  The 
stimulus  of  light  on  the  retina  produces  contraction  of  the 
circular  tibres  of  the  iris,  and  partial  closure  of  the  ])upil. 
This  is  a  reflex  action,  the  stimulus  being  conveyed  by  tho 
optic  nerve  to  the  brain,  and  thence  reflected  through  the 
third  nerve  to  tho  iris;  consequently  tho  iris  ceases  to  act 
when  cither  the  optic  or  third  nerve  is  divided  or  destroyed^ 
or  the  nervous  centre  injured  or  compressed.  The  rad'uUivg 
fibres  of  tho  iris  are  supplied  by  filaments  from  the  fifth 
cranial  nerve  and  the  ophthalmic  or  ciliary  ganglion. 

The  jtaUietic  nerve,  the  smallest  of  the  cranial  nerves,  is 
also  a  nerve  of  motion  distributed  to  the  suj)orior  obli(jue 
muscle.  When  the  nerve  is  irritated  the  muscle  acts  spas- 
n\odically,  and  its  division  causes  paralysis  and  a  loss  of 
rotatory  motion  of  the  eyeball  on  its  axis,  and  sometimes 
double  vision 

The  abdacens  supplies  the  external  rectus  with  motor 
power.  Irritation  of  this  nerve  produces  convulsion  of  the 
muscle,  and  the  eye  is  turned  outwards.  Division  or  injury 
is  followed  by  convergent  strabismus. 

The  trifacial  nerve  closely  resembles  the  spinal  nerves. 
It  arises  by  two  roots  an  anterior,  smaller  or  motor,  and  a 
posterior  or  sensory,  wliich  has  a  ganglion  (the  Gasserian 
ganglion)  developed  on  it.  The  functions  of  this  nerve  are 
various  ;  it  is  the  great  sensitive  nerve  of  the  head  and 
face ;  the  motor  nerve  of  the  muscles  of  mastication  (except 
the  buccinator),  and  its  lingual  branch  is  one  of  the  nerves 
of  the  special  sense  of  taste.  This  nerve,  within  the  cran- 
ium, is  divided  into  three  branches — the  ophthalmic,  which 
passes  through  the  sphenoidal  fissure,  the  superior  max- 
illa'i'y,  which  passes  through  the  foramen  rotundum,  and 
the  inferior  maxillary,  which  passes  through  the  forainen 
ovale.  The  first  and  second  divisions  are  purely  sensory ; 
19 


332 


THE  NERVOUS  SYSTEM. 


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Mr. 

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the  third  division  contains  filaments  of  special  sense,  sensa- 
tion and  motion.     It  is  the  most  intensely  sensitive  nerve  in 
the  body,  and  irritation  of  its  sensory  filaments  is  followed 
by  intense  pain.     Any  irritation  to  this  nerve,  or  any  of  its 
branches,  as  e.  (j.,  a  carious  tooth,  may  give  rise  to  neuralgia 
of  the  corresponding  side  of  the  face,  and  in  many  instances 
one-half  of  the  tongue  is  found  covered  with  a  white  fur, 
while  the  other  half  is   perfectly  clean.      Division  of  the 
fifth  nerve   produces  loss  of  sensibility  and  motion  in  the 
parts  supplied  by  it,  and  is  followed  by  inflammation  of  the 
corresponding  eye ;  the  cornea   becomes  opaque,  and  a  low 
destructive  inflammation  of  the  conjunctiva,  sclerotic,  and 
interior  of  the  eye  occurs,  which  usually  goes  on  to  complete 
and  permanent  destruction,  and  sloughing  of  the  organ ;  the 
senses  of  smell,  hearing,  and  taste,  are  at  the  same  time  im- 
paired or  lost.      Injury  to  the  fifth  nerve,  or  some  of  its 
branches,  is  sometimes  followed  by  total  blindness  in  the 
corresponding  eye.     These  phenomena  may  be  due  to   the 
trophic  influence  of  the  nerve  on  these  organs,  and   the 
defective  nutrition  which  follows  its  injury.     Paralysis  of 
the  third  nerve  may  also  follow  neuralgia  of  the  fifth  nerve. 
The  facial  newe  (fortio  dura)  supplies  all  the  muscles  of 
the  face,  the  platysma,  buccinator,  the  muscles  of  the  ex- 
ternal ear,  digastric  and  stylo-hyoid,  the  palate,  stapedius 
and  laxator  tympani  muscles.     It  also  supplies  the  parotid 
gland,  and  through  the  chorda  tympani  it  gives  branches 
to  the  submaxillary  gland,  lingualis,  and  other  muscles  of 
the  tongue.     It  is  a  nerve  of  motion,  and  not  of  sensation, 
and  therefore  its  division,  which  was  formerly  resorted  to 
in  "ases  of  tic  douloureux,  is  incapable  of  relieving  neuralgic 
r  »ut  is  followed  by  paralysis  of  the  muscles  which  it 

les.     Division  or  paralysis   of   the  facial  nerve  pre- 
onts  the  eye  from  being  closed,  and  its  continued  exposure 
to  the  air,  and  particles  of  dust,  is  apt  to  produce  inflam- 
mation.    The  sense  of  hearing,  taste,   and  smell  may  also 
be  impaired.     In  facial  paralysis  there  is  an  absence  of 


GLOSSO-PHA  R  YNGEAL  NER  VE. 


333 


€xi)re8sion  on  the  affocted  side,  the  angle  of  the  mouth  is 
lower,  and  the  eye  has  an  unmeaning  stare.  In  drinking, 
the  fluids  flow  out  at  the  corner  of  the  mouth,  and  the  food 
lodges  between  the  clieek  and  gums.  Wlieu  the  tongue  is 
paralyzed,  it  is  drawn  to  the  sound  side  when  protruded,  in 
consequence  of  tiie  paralysis  of  the  muscles  on  the  aflected 
side. 

The  glosso -pharyngeal  7ierve  is  distributed  to  the  tongue 
and  pharynx,  being  the  nerve  of  sensation  to  the  mucous 
membrane  of  the  pharynx,  the  fauces  and  tonsil  ;  of  motion 
to  the  pha'yngeal  muscles,  and  a  special  nerve  of  taste  to 
the  posterior  part  of  the  tongue.  It  also  supplies  filaments 
to  the  fenestra  ovalis  and  rotunda,  the  Eustachian  tube,  car- 
otid plexus,  and  spheno-palatine  ganglion.  The  tongue  is 
supplied  by  two  special  nerves — the  lingual  branch  of  the 
fifth,  and  the  glosso-pharyngeal ;  the  former  supplies  the 
anterior  and  lateral  parts  of  the  superior  surface,  and  the 
latter  the  posterior  and  lateral  parts.  This  may  be  proved 
by  division  of  either  of  these  nerves,  when  the  sense  of 
taste  is  lost  in  the  part  supplied  by  the  injured  nerve. 

The  hypoglossal  nerve  is  a  nerve  of  motion.  It  is  dis- 
tributed to  the  muscles  which  belong  to  the  hyoid  bone  and 
tongue,  and  is  concerned  in  articulation.  Irritation  of  this 
nerve  produces  contraction  in  the  muscles  supplied  by  it, 
and  is  sometimes  attended  with  pain,  the  sensibility  having 
been  borrowed  from  the  nerves  with  which  it  communi- 
cates.    Its  division  or  injury  is  followed  by  paralysis. 

The  pneumogastric  nerve  is  one  of  ihe  most  remarkable 
and  important  in  the  body.  It  supplies  the  pharnyx,  epi- 
glottis, glottis,  larynx,  trachea,  oesophagus,  heart,  lungs, 
liver,  stomach  and  spleen.  It  possesses  motor,  sensitive 
and  sympathetic  or  ganglionic  nerve  fibres,  and  is  therefore 
regarded  as  a  triple-mixed  nerve.  The  pharyngeal  branch  is 
the  motor  nerve  of  the  muscles  of  the  pharynx  ;  the  superior 
laryngeal  is  chiefly  sensory,  and  supplies  the  mucous  mem- 
brane of  the  larynx ;   the  inferior  or  recurrent  laryngeal 


jll 


334 


THE  NERVOUS  SYSTEM. 


c 
c 

I 

m 
I 

r 

k 

larr 
SCI 


is  for  the  most  part  motor,  and  supplies  tlie  muscles;  the 
oesoj^hageal  branches  supply  its  muscular  tissue  ;  the  cardi- 
ac branches  constitute  a  channel  through  which  the  influ- 
ence of  the  central  organs  and  the  emotions  of  the  mind  are 
transmitted  to  the  heart ;  the  pulmonary  branches  form  a 
channel  through  which  the  impressions  on  thelungsaro  convey- 
ed to  the  medulla  oblongata;  the  motor  filaments  of  the  pneu- 
mogastiic  nerve  supply  the  motor  influence  by  which  the 
function  of  deglutition  is  performed.  In  the  functions  of 
the  larynx,  the  sensitive  filaments  suppl}'^  that  acute  sensi- 
bility by  which  the  glottis  is  guarded  against  the  ingress  of 
foreign  bodies  or  irrespirable  gases.  These  are  instances 
of  "  reflex  action." 

The  cardiac  branches  of  the  pneumogastric  have  an  in- 
/tivcvO?'?/ or  restraining  influence  upon  the  heart  (p.  212). 
When  divided  the  heart's  action  is  increased ;  while  on  tlio 
other  hand  when  stimulated,  as  by  a  galvanic  cuirent,  the 
heart's  action  is  diminished,  or  if  a  strong  current  be  used, 
it  is  arrested  altogether  in  diastole. 

Division  of  the  pneumogastric  nerve  or  its  inferior  laryn- 
geal branches  produces  loss  of  voice,  by  paralyzing  the 
riiuscles  of  the  larynx  which  act  upon  the  vocal  chords, 
Di  visioL  of  the  pneumogastric  nerves  is  also  followed  by  a 
diminution  of  the  frequency  of  the  respiratory  movements. 
In  young  animals  it  is  often  quickly  fatal,  owing  to  the 
closure  of  the  glottis,  which  is  due  to  the  yielding  nature  of 
the  cartilages;  but  in  older  animals  death  ensues  more  slowly, 
owing  to  the  rigidity  of  the  cartilages  wdiich  surround  the 
glottis.  Death  takes  ])lace  in  from  one  to  six  days  after  the 
operation,  and  is  caused  by  the  engorgement  of  the  lungs. 
They  are  commonly  very  much  congested,  nearly  solid, and 
the  bronchial  tubes  are  filled  with  a  frothy,  bloody  fluid,  and 
mucus.  This  is  due  in  part  to  the  slowness  of  the  respira- 
tory movements,  the  imperfect  aeration  of  the  blood,  and 
the  accumulation  of  carbonic  acid  in  the  air  cells,  and  also 
in   part  to  the  paralysis  of  the   blood-vessels  themselves. 


ungs. 
J,  and 
d.and 
spira- 
d,  and 
d  also 
elves. 


PNEUMOGASTRIC  NERVE. 


335 


Since  respiration  is  still  carried  on  after  the  division  of  the 
pneumogastric  nerves,  it  is  evident  that  though  they  are  the 
chief  agents  by  which  the  respiratory  stimulus  is  conveyed 
to  the  medulla  oblongata,  they  are  not  the  only  ones. 

The  secretion  of  gastric  juice  is  temporarily  suspended 
after  division  of  the  pneumogastric  nerve,  and  the  digestive 
function  is  more  or  less  disturbed  in  various  wavs,  but  the 
sensations  of  hunger  and  thirst  still  remain.  In  many  in- 
stances the  food  taken  by  the  animal  never  reaches  the 
stomach  owing  to  the  paralysis  of  the  cesophagus,  but  is  re- 
gurgitated in  a  few  moments  afterwards — this  action  being 
excited  by  the  influence  of  the  sympathetic  nerves.  The 
muscular  coat  of  the  stomach  is  also  paralyzed  by  section  of 
this  nerve. 

Division  of  the  pneumogastric  nerve  also  interferes  with 
the  proper  function  of  the  liver,  and  irritation  of  the  cen- 
tral extremity  of  the  divided  nerve  is  followed  by  the  rapid 
development  of  sugar  in  this  organ,  probably  \sy  causing 
paralysis  of  the  hepatic  vaso-motor  nerves. 

The  sjnnal  accessory  nerve  arises  ])artly  from  the  medul- 
la oblongata,  and  jiartly  from  the  spinal  cord.  It  is  essen- 
tially a  motor  nerve;  but  it  also  contains  sensitive  fibres, 
and  is  connected  with  the  ganglion  of  the  pneumogastric. 
From  these  circumstances  it  may  be  regarded  as  a  mixed 
nerve.  It  supplies  the  sterno-mastoid  and  trapezius  mus- 
cles, and  it  is  also  connected  with  the  vocal  movements  of 
the  glottis.  If  the  spinal  accessory  nerve  be  divided  on 
both  sides,  or  its  branch  of  communication  with  the  pneu- 
mogastric nerve,  the  voice  is  instantly  lost,  the  animal  be- 
ing incapable  of  uttering  a  single  sound.  Division  of  the 
pneumogastrics  or  their  inferior  laryngeal  branches,  para- 
lyzes both  the  movements  of  respiration  and  phonation, 
while  section  of  the  spinal  accessory  paralyzes  the  move- 
ments of  phonation  alone,  or  those  muscles  which  nar- 
row the  glottis  and  ai)proximate  the  vocal  chords,  the 
movements  of  respiration,  which  open  the  glottis  and  sepa- 


336 


THE  NERVOUS  SYSTEM. 


c 
t 

IIB 

L 

»» 

M 
I 


rate  the  vocal  chords  remaining  intact.  It  may  be  stated 
as  a  general  law,  that  when  any  part  of  the  body  receives 
nervous  lilaments  from  two  different  sources,  it  is  for  the 
purpose  of  enabling  it  to  perform  two  different  functions. 
This  is  exemplified  in  the  muscles  of  the  larynx.  These 
muscles  are  concerned  in  the  respiratory  movements,  the 
nervous  stimulus  for  which  is  conveyed  by  the  facial,  hypo- 
glossal, and  pneumogastric  nerves;  but  they  are  also  con- 
cerned in  the  formation  of  the  voice,  the  nervous  influence 
for  which  is  conveyed  by  the  spinal  accessory. 

SYMPATHETIC   NERVOUS    SYSTEM. 

The  sympathetic  system  (or  nervous  system  of  organic 
life),  is  so  named  because  it  was  formerly  supposed  to  be 
the  system  through  which  distant  organs  manifested  sym- 
pathy with  each  other  in  morbid  action.  It  consists  of  a 
series  of  ganglia  connected  together  by  intervening  cords, 
extending  on  each  side  of  the  spinal  column,  from  the  base 
of  the  skull  to  the  coccyx  ;  some  of  the  ganglia  may  also  be 
traced  into  the  cranium.  These  two  gangliated  cords  lie 
parallel  to  one  another  as  far  as  the  coccyx,  where  they 
communicate  through  a  single  ganglion — ganglion  mipar. 
It  is  also  stated  that  they  communicate  at  their  cephalic 
extremity  through  a  small  ganglion,  situated  on  the  anter- 
ior communicating  artery — the  ganglion  of  Ribes. 

They  are  arranged  as  follows : — In  the  cephalic  region 
there  are  four  ganglia  on  each  side  (and  the  ganglion  of 
Ribes);  in  the  cervical  region,  three;  in  the  dorsal  region, 
twelve ;  in  the  lumbar  region,  four ;  in  the  sacral  region, 
five ;  and  in  the  coccygeal  region,  one — the  ganglion  impar. 
Each  ganglion  may  be  regarded  as  a  distinct  centre  from 
and  to  which,  branches  pass  in  various  directions,  as  follows 
— 1st,  communicating  branches  between  the  ganglia  ;  2nd, 
communicating  branches  to  the  cerebral  or  spinal  nerves ; 
3rd,  primary  branches  of  distribution  to  the  arteries  in  the 
vicinity  of  the  ganglia,  to  the  viscera,  or  to  other  ganglia  in 


THE  SYMPATHETIC  SYSTEM. 


337 


iu  the 


the  thorax,  abdomen,  and  pelvis.  The  latter  consist  of  two 
kinds  of  nerves,  the  syr)i2iathetic  and  spinal,  and  have  a 
remarkable  tendency  to  form  intricate  plexuses  which  sur- 
round bhe  blood-vessels,  being  conducted  by  them  to  the 
viscera.  Many  of  these  primary  branches,  however,  pass 
to  a  series  of  ganglia  in  the  thorax  and  abdomen,  the  chief 
of  which  are  the  cardiac  and  semilunar  ganglia.  Fibres 
of  the  sympathetic  are  distributed  to  the  nonstriated 
muscular  tissue  of  the  intestines  and  other  hollow  organs, 
and  to  the  blood-vessels  (vaso-motor  nerves) ;  to  the 
heart — excito-motor ;  and  to  the  various  glands.  Centripe- 
tal fibres  also  pass  to  the  vaso-motor  centre  in  the  medulla 
oblongata.  The  difference  between  the  cerebro-spinal  and 
sympathetic  nerves  has  been  already  stated  (p.  282).  Both 
kinds  of  nerves  are  distributed  to  ail  parts  of  the  body. 

The  ganglia  of  the  sympathetic  system  are  regarded  by 
some  writers  as  reservoirs  of  nervous  force,  which  they 
equalize  and  correctly  balance,  by  storing  up  all  transient 
excesses,  and  furnishing  all  transient  deficiencies.  In  struc- 
ture they  are  essentially  similar,  containing  nerve  fibres 
entering  and  emerging,  nerve  cells,  or  ganglion  corpuscles, 
and  other  corpuscles  that  appear  free  (Fig.  08).  Comi)lex 
as  the  whole  sympathetic  system  appears,  however,  each  of 
its  parts  exhibits  a  wonderful  simplicity;  for  each  ganglion 
with  its  afi'erent  and  efferent  nerves  forms  a  simple  nervous 
system,  and  might  serve  for  the  illustration  of  all  the  ner- 
vous actions  with  which  the  mind  is  unconnected. 

Function  of  the  Sympathetic  System. — The  sympa- 
thetic nervous  system  is  endowed  with  sensibility  and 
the  power  of  exciting  motion  exactly  similar  to  the  cerebro- 
spinal system  ;  but  in  the  exercise  of  these  functions  it  is 
less  active.  When  irritation  is  applied  to  a  sensitive  nerve 
in  one  of  the  extremities,  the  evidence  of  pain  or  motion  is 
acute  and  instantaneous  ;  while,  on  the  other  hand,  irrita- 
tion of  the  sympathetic  nerve  is  felt  distinctly  enough,  but 
is  only  responded  to  after  somewhat  prolonged  application. 


S38 


THE  NERVOUS  SYSTEM. 


mK^--W 


C 
t 

t 

tn 
I 

I* 
I 

c 
c 

^\ 

m 


This  comports  very  much  with  what  is  known  of  those 
organs,  supplied  chiefly  by  the  sym})athetic  system,  e.  g., 
the  movements  of  the  stomach  and  intestines  are  not  felt 
under  ordinary  circumstances;  but  any  excessive  or  pro- 
longed irritation  maj'  cause  them  to  be  exceedingly  painful. 
The  general  processes  which  the  sympathetic  system  ap- 
pears to  influence  are  those  of  involuntary  motion,  secretion, 
and  nutrition.  The  ganglia  have  the  power  of  conducting, 
transferring  and  reflect Ing  impressions  made  on  them  simi- 
lar to  the  cerebro-spinal  system,  and  the  sympathetic 
nerves  are  conductors  of  impressions.  Parts  chiefly  suppli- 
ed with  sympathetic  nerves  are  usually  capable  of  only 
involuntary  movements,  as,  e.g.,  the  heart,  stomach  and  in- 
testines, and  these  parts  may  still  continue  to  move  for  a 
short  time  after  the  death  of  the  animal.  Thus,  in  the 
mammalia  the  heart  continues  to  beat  for  one  or  two 
minutes  after  it  is  taken  from  the  body  ;  in  reptiles  and 
amphibia  for  several  houis  ;  and  the  peristaltic  action  of 
the  bowels  is  continued  for  a  prolonged  period. 

Division  of  the  sympathetic  nerve  produces  immediately 
a  vascular  congestion  in  the  parts  supplied  by  it.  This 
was  first  pointed  out  by  Bernard ;  he  divided  the  sym- 
pathetic nerve  of  a  rabbit  in  the  middle  of  the  neck,  and 
found  that  congestion  of  the  corresponding  side  of  the  head 
immediately  followed,  which  was  most  distinctly  marked 
in  the  ears  ;  and  the  venous  blood  returning  from  the  part 
had  a  ruddy  hue.  The  pupil  is  also  contracted  and  the  eye 
partially  closed,  ov/ing  to  the  increased  sensibility  of  the 
retina  from  vascular  congestion  of  the  parts.  The  conges- 
tion appears  to  be  caused  by  the  dilatation  of  the  vessels 
and  consequent  increased  rapidity  of  the  circulation,  for 
when  any  irritation  is  a])plied  to  the  divided  end  of  the 
nerve,  the  vessels  contract  and  the  congestion  disappears. 
The  vessels  therefore  appear  to  be  under  the  influence  of 
the  sympathetic  nerves,  which  accompany  them  in  all  their 
varied    distributions  and  minute  ramifications.     They  are 


nges- 
ssels 
for 
the 
Dears, 
e  of 
their 
are 


THE  SYMPATHETIC  SYSTEM. 


339 


distributed  to  the  muscular  coat  of  the  vessels,  the  function 
of  which  is  to  regulate  the  supply  of  blood  to  the  various 
organs.  The  congestion  of  the  vessels  caused  by  division 
of  the  sympathetic  nerve  is  also  accompanied  by  an  eleva- 
tion of  temjieratiire  in  the  affected  part ;  this  increase 
of  heat  has  been  found  as  high  as  8°  to  9°F.,  and  like  the 
vascular  congestion,  to  which  it  is  due,  may  last  a  consider- 
able length  of  time.  The  sympathetic  system  has  also 
some  connection  with  the  special  senses,  especially  with  the 
sense  of  sight.  The  ophthalmic  ganglion  gives  off'  small 
branches  t(i  the  iris,  and  receives  a  communicating  motor 
branch  from  the  third  nerve.  The  contraction  of  the  pupil 
under  the  influence  of  light,  and  its  dilatation  in  the  dark, 
are  affected  through  this  ganglion. 

With  reference  to  the  influence  of  the  sympathetic  nerve 
in  the  processes  of  secretion  and  nutrition,  little  is  known 
except  that  it  is  in  great  measure  connected  with  the 
supply  of  blood  to  the  parts.  It  serves  as  a  medium  of 
reflex  action  between  the  sensitive  and  motor  portions  of 
the  digestive,  excretory  and  generative  organs,  and  it  also 
takes  part  in  reflex  actions  which  may  be  referred  to  the 
cerebro-spinal  system  ;  foi-  example,  the  contact  of  food  in 
the  intestine  excites,  through  the  medium  of  the  sympa- 
thetic nerves,  a  peristaltic  movement  in  the  muscular  coat. 
The  irritation  produced  by  undigested  food  in  the  ali- 
mentary canal  may  give  rise  to  diarrhoea,  or  it  may  produce, 
through  the  medium  of  the  sympathetic  and  cerebro-spinal 
systems,  epileptic  convulsions,  especially  in  children. 


a4() 


THE  SPECIAL  SENSES, 


C\[\VT¥Al  XIV. 


C 

t 

•i« 

•t 
M 

I 

r 

Hi 


or. 


TllK    SI'KCIAL    SKNSES. 

The  spocial  senses  avajive  in  number, i^iiieU,^ I <jht_  hearing, 
taste,  and  iouclt.  The  hist  two  liave  been  aheacly  casually 
referred  to. 

SjMKLF.. — The  sense  of  smell  is  limited  to  the  nasal  cavity, 
and  is  confined  to  that  poition  on  which  the  olfactory 
nerves  are  distributed,  viz.,  the  roof,  the  septum,  and  the 
upper  part  of  the  lateral  walls  (Fig.  110,  p.  330).  The  na.sal 
cavity  is  lined  by  mucous  mond)rane,  called  also  the 
pituitary  or  Schnaiderian  mend)rane ;  it  is  covered  with 
columnar  ciliated  epithelium,  except  in  the  upper  part  and 
roof — the  olfactory  i-egion,  in  which  it  is  non-ciliated. 
The  filaments  of  the  olfactoiy  nerves  pass  through 
the  foramina  in  the  cribriform  plate  of  the  ethmoid  bone, 
and  are  ilistributed  beneath  the  mucous  membrane ;  they 
convey  the  sensitive  impressions  made  by  odoriferous 
particles  upon  the  nuicous  membrane  to  the  sensorium, 
which  give  rise  to  the  sense  of  smell.  The  sense  of  smell 
is  confined  to  the  olfactory  nerves,  as  has  been  shown  by 
their  division,  after  which  the  sense  of  smell  is  completely 
lost,  while  sensibility  still  remains,  and  their  irritation  is 
not  followed  by  any  musculai"  action,  either  of  a  uirect  or 
reflex  character.  Division  of  the  fifth  nerve,  or  some  of  its 
branches,  which  suppl}'  the  nose,  is  followed  by  impairment 
of  the  sense  of  smell.  It  cannot  be  inferred  from  this,  how- 
ever, that  it  is  a  nerve  of  the  special  sense  of  smell  ;  the 
result  is  to  be  attributed  to  the  dry  and  otherwise  deranged 
state  of  the  mucous  membrane,  occasioned  by  the  altered 
nutrition  of  the  parts. 


SENSE  OF  SME/J.. 


841 


The  meatuses  and  sinuosities  of  the  nasal  cavities  are 
well  adapted  not  only  to  increase  the  extent  of  mucous 
•surface,  but  also  to  injpcde  the  air  and  odoriferous  particles 


V\)i'  111; 


^ 


Nose,  mouth  and  pliar.viix  ;  u,  cribrifonii  plate  ;  b,  spine  ;  c,  soft  palate  ;  d,  lower  jaw  ;  e, 
hyoid  bone  ;  f,  cavity  of  the  larynx  ;  1,  ton}f\ic  ;  m,  n,  o,  s\i]>eri<)r,  middle  and  nferior 
turbinated  bones,  beneath  which  lire  the  meatuses  ;  q,  frontal  sinuses  ;  s,  narrow  part  of 
thepliarynx;  t,  tonsil ;  u,  anterior  |)illar  of  the  fauces;  v,  ixi.sterior  pillar;  y,  tlio  epi- 
glottis ;  z,  orifice  of  the  Eustachian  tulx!. 

which  it  may  contain,  in  their  passage  through  them,  so  as 
to  bring  them  into  more  immediate  contact  with  the  mucous 
surface,  by  means  of  which  their  peculiar  characters  are 
more  fully  impressed  on  the  olfactory  nerves.  1^\\q  frontal 
sinuses  are  supposed  to  assist  in  the  extension  of  the  sense 
of  smell ;  but  since  they  do  not  receive  filaments  from  the 
olfactory  nerves,  and  are  largely  developed  in  some  animals, 


342 


THE  SPECIAL  SENSES. 


c 
t 

I. 

Ih 

K 

L 


iWi' 

OH 


as  the  grey-hound,  in  which  the  sense  of  smell  is  by  no 
means  acute,  it  is  highly  improbable.  The  sense  of  smell 
varies  much  in  different  individuals,  and,  like  all  the  senses, 
may  be  improved  by  frequent  practice. 

It  may  become  blunted  by  long-continued  exposure  to 
one  kind  of  smell,  as,  for  example,  the  effluvia  of  the  dis- 
secting room.  Various  odors  also  affect  it  differently,  as 
musk,  asafoetida ;  and  some  produce  nausea  and  even 
fainting. 

The  irritation  produced  by  the  contact  of  substances 
which  act  mechanically  or  chemically  on  the  mucous  mem- 
brane, as  ammonia,  nitrous  acid,  etc.,  must  not  be  confounded 
with  the  sense  of  smelling.  These  impressions  are  conveyed 
to  the  sensorium  by  the  fifth  nerve,  which  is  the  nerve  of 
sensation.  The  sense  of  smell  may  be  impaired  or  destroyed 
by  a  dry  state  of  the  mucous  membi'ane  ;  by  the  obstruction 
of  the  air  passages,  as  in  the  case  of  polypi ;  by  chronic  in- 
flanmiation,  as  catarrh,  oziena,  and  by  the  frequent  use  of 
finuff,  which  tends  to  blunt  its  acuteness  and  cover  the  sur- 
face with  its  particles. 

Besides  the  olfactory  and  fifth  nerve,  there  are  some  fila- 
ments from  the  spheno-palatine  ganglion  distributed  to  the 
nose.  The  function  of  these  is  not  very  well  known  ;  but 
from  the  connection  with  the  fiftli  nerve  and  the  sympathy 
between  the  sense  of  smell  and  taste,  they  are  probably 
nerves  of  associate  function.  All  animals  have  not  the 
same  facility  for  perceiving  odors.  Carnivorous  animals 
have  the  faculty  of  detecting  readily,  animal  odors,  and 
tracking  other  animals  by  the  scent.  Herbivorous  animals, 
on  the  other  hand,  possess  the  power  of  detecting  readily 
the  odor  of  vegetable  matters.  The  sense  of  smell  in  man 
is  not  so  acute  as  in  most  animals,  but  it  is  more  uniform 
and  extended.  The  extreme  delicacy  of  the  sense  of  smell 
is  shown  by  the  fact,  that  ao.wTjV.ooo  of  a  grain  of  musk  may 
be  distinctly  smelt.  Some  odors  are  pleasant,  and  some  are 
oH'onsive,  but  the  cause  of  the  difference  is  not  known ;  many 


SENSE  OF  SIGHT. 


34a 


odors  also  which  are  agreeable  to  one  individual,  are  ofien- 
sive  to  another.  Certain  sensations  also  frequently  produce  a 
smell,  for  example,  electricity  produces  a  smell  like  phos- 
phorus, and  the  negative  pole  of  the  battery  applied  to  the 
nose  a  smell  of  ammonia  ,  while  the  positive  pole  produces  an 
acid  odor.  In  disease  or  derangement  of  the  olfactory  nerve, 
subjective  sensations  of  smell  frequently  occur. 

SIGHT. 

The  eye  is  the  organ  of  the  special  sense  of  sight,  and  is 
situated  in  the  cavity  of  the  orbit.  It  is  ^pherical  in  form, 
having  the  segment  of  a  smaller  and  more  prominent  sphere 
engrafted  on  its  anterior  surface.  It  measures  about  an 
inch  in  the  antero-posterior  diameter,  and  a  little  less  trans- 
versely. It  consists  of  three  coats :  an  outer,  consisting  of 
the  sclerotic  and  cornea ;  a  middle,  consisting  of  the  choroid 
coat,  ciliary  processes,  and  iris ;  and  an  internal,  the  retina  ; 
and  three  refracting  media, — the  aqueous  humor,  the  vitreous 
humor,  and  the  crystalline  lens  and  capsule. 

The  sclerotic  is  a  dense  fibrous  membrane,  thicker  behind 
than  in  front,  which  covers  the  ])osterior  five-sixths  of  the 
eye.  It  is  continuous  in  front  with  the  cornea,  and  behind 
with  the  sheath  of  the  optic  nerve,  which  is  derived  from 
the  dura  mater.  Behind,  it  is  pierced,  a  little  to  its  nasal 
side,  by  the  optic  nerve,  around  which  are  openings  for  the 
passage  of  the  ciliary  vessels  and  nerves. 

The  cornea  projects  forwards,  somewhat  resembling  a 
watch-glass,  and  covers  the  anterior  sixth  of  the  globe.  It 
is  concavo-convex,  the  degree  of  curvature  varying  in  dif- 
ferent individuals,  and  in  the  same  individual  at  different 
periods  of  life,  being  generally  more  prominent  in  youth 
than  in  advanced  age.  This  diffTerencein  the  curvature  in- 
fluences considerably  the  refractive  power  of  the  eye, 
and  is  partlj''  the  cause  of  long  and  short-sightedness. 
The  cornea  in  health,  is  perfectly  transparent,  contains  no 
bloodvessels,  and  consists  of  five  layers; — the  cornea  proper, 


11 


'i 


344 


THE  SPECIAL  SENSES. 


c 


r 

«1 


iBr* 

'V.I, 


Vertical  tiecition  of  the  eye  ball.  1,  sclerotic;  2,  choroid; 
3,  retina;  4,  crystalline  lens;  5,  hyaloid  membrane;  6, 
cornea ;  7,  iris ;  8,  vitreous  body. 

elastic    lamirife,    consist    of 


a  central  fibrous  structure ;  in  front  of  this,  the  anterior 
elastic  lamina,   covuied   by  the  conjunctiva;  behind,  the 

posterior  elastic  la- 
mina, covered  by 
the  lining  mem- 
brane of  the  an- 
terior chamber  of 
the  eyeball.  The 
conjunctival  epithe- 
lium consists  of  sev- 
I'lal  layers  of  cells, 
the  superficial  ones 
being  flattened  and 
scaly,and  the  deeper 
ones  columnar  or 
cylindrical.  The  an- 
terior and  posterioi" 
laminfe,  consist  of  a  thin,  transparent  homo- 
genous membrane,  and  have  a  tendency  to  curl  upon 
themselves,  with  the  attached  surface  inwards,  when 
separated  from  the  cornea  proper.  The  cornea  pro- 
per coLsists  of  finely  fibrillated  bundles  of  transpa- 
rent connective  tissue,  in  the  spaces  of  which  the 
branched  cornea  corpuscles  lie.  The  branched  cornea  cor- 
puscles are  capable  of  passing  from  one  space  to  another  by 
their  amoeboid  movement.  When  this  tissue  is  injured  in 
any  way,  it  presents  an  opaque  milky  appearance.  The 
posterior  elastic  lamina  and  the  single  layer  of  epithelium 
which  covers  it,  is  known  as  Descemet's  membrane.  The 
nerves  that  supply  the  cornea  are  derive'^1  from  the  ciliary 
nerves. 

The  choroid  is  a  thin,  highly  vascular  membrane,  of  a 
dark  color,  which  covers  the  posterior  five-sixths  of  the 
globe,  and  is  situated  between  the  sclerotic  and  retina.  It 
is  pierced  behind  by  the  optic  nerve,  and  terminates  in  front 
at  the  ciliary  ligament,  where  it  bends   inwards  and  forms 


ff 


SENSE  OF  SIGHT. 


34.5 


upon 
when 


the  ciliary  processes.  It  is  com])osecl  of  three  layers,  the 
emternal,  which  consists  of  the  larger  branches  of  the  ciliary 
arteries,  but  chiefly  tlie  veins  and  some  star-shaped  pigment 
cells;  the  middle,  which  consists  of  a  fine  capillary  plexus 
(tunica  Ruyschiaui) ;  and  the  internal  or  pigmentary  \a.yer, 
which  is  made  up  of  a  single  layer  of  hexagonal  cells,  loaded 
with  pigment  granules,  so  arranged  as  to  resemble  tesselated 
epithelium.  The  principal  use  of  the  choroid  coat  is  to  ab- 
sorb the  rays  of  light  which  pass  through  the  retina,  and 
prevent  them  from  being  thrown  back  to  dazale  the  images 
formed  on  the  retina.  In  perfect  Albinoes  the  cells  contain 
no  pigment,  and  they  can  s-^e  best  in  moderate  light,  or  twi- 
light. 

The  ciliary  processes  are  formed  by  the  folding  inwards 
of  the  middle  and  internal  layers  of  the  choroid  around  the 
margin  of  the  lens,  behind  the  iris.  They  vary  in  number 
from  sixty  to  eighty,  and  are  about  one-tenth  of  an  inch  in 
length.  They  are  similar  in  structure  to  the  correaponding 
layers  of  the  choroid. 

The  iris  (tpii,  a  rainbow)  is  a  thin,  circular-shaped  con- 
tractile curtain  which  regulates  the  quantity  of  light  trans- 
mitted to  the  retina.     It  is  suspended  in  the  aqueous  humor 
behind  the  cornea,  and  in  front  of  the  lens,  and  presents, 
at  the  nasal  side  of  its  centre,  a  circular  opening,  the  pupil, 
for  the  transmission  of  light.      It  separates  the  cavity  for 
the  aqueous  humor  into  two  parts,  the  anterior  and  posterior 
chambers.     It  consists  of  a  fibrous  stroma,  Tnuscular  fibres, 
and  pigment  cells.     The  muscular  tissue  is  involuntary  and 
consists  of  circular  fibres  which   surround  the  pupil,  and 
radiating  fibres  which  converge  from  the  circumference  of 
the  iris  to  the  margin  of  the  pupil ;  the  former  contract 
the  pupil,  the  latter  dilate  it.     The  circular  fibres  are  sup- 
plied by  the  third  cranial  nerve,  and  the  radiating  fibres  by 
the  fifth  and  sympathetic  (p.  331).     The  fibrous  tissue  forms 
a  delicate  net-work  in  which  the  pigment  cells,  vessels  and 
nerves  are  contained.     The  pigment  cells  are  found  in  the 


346 


THE  SPECIAL  SEASES. 


stroma,  and  also  as  a  distinct  layer  on  the  anterior  and 
posterior  .surfaccH,  and  j^ive  rise  to  the  different  coh)r  of  the 
iris  in  dirtbront  individuals.  On  blic  posterior  surface  of  the 
iris  there  are  several  layers  of  round  cells  filled  with  pig- 
ment granules.  These  are  called  the  uvea,  from  their  resem- 
blance in  color  to  a  ripe  grape.  The  iris  is  connected  to  the 
choroid  and  to  the  external  coat  of  the  eyeball  at  tlie  junc- 
tion of  the  sclerotic  and  cornea,  by  means  of  a  circular  band 
of  white  fibi-ous  tissue,  the  ciliary  li(j<iinent.  At  its  point 
of  junction  with  the  sclerotic  a  minute  canal  is  seen,  the 
sinus  circularia  iridis. 

The  middle  coat  of  the  eye  is  also  connected  to  the  exter- 
nal, by  ni<;ans  of  a  circular  band  of  nonstriated  muscular 


Ki-.  n:t. 


•v 


r 

F 


tissue,  the  ciliary  muscle.  It  is  about  one-eighth  of  an  inch 
broad,  thicker  in  front  than  behind,  and  is  attached  ante- 
riorly, or  arises  at  the  point  of  junction  of  the  sclerotic  and 


H 


SENSE  OF  S/G^T. 


M7 


cornoa,  aiul  paHsiiig  backwards  is  iuserfed  into  the  clioioid 
in  front  of  tlio  rotina.  By  its  action  it  draws  tlie  ciliary 
Iirocosses  towards  the  lino  of  junction  of  the  sclerotic  and 
cornea,  and  compresses  the  lens,  increasing  the  ciu'vature  of 
its  anterior  surface,  and  in  this  way  adjusting  the;  eye  to  the 
vision  of"  near  objects. 

The  reflna  h  the  delicate  nervous  nienibrane  upon  tlie 
Hurlace  of  which  the  images  of  external  objects  are  received. 
Beliind,  it  is  continuous  with  the  optic  nerve  ;  in  front  it 
terminates  by  a  serrated  margin,  the  ora  serrata  ;  its  inner 
!-urface  is  in  contact  with  the  hyaloid  membrane  which  sur- 
rounds the  vitreous  humor;  ext(jrnally  it  is  in  I'elation  with 
tlte  choroid.  In  the  centre  of  the  posterior  part,  correspond- 
ing to  the  axis  of  the  eye,  is  seen  a  round,  yellowisli  spot 
/•,  of  an  inch  in  diameter  (1  mm.)  called  the  llmhus  lideus, 
or  the  yellow  sj)ot  of  Sommering.  In  its  centre  is  a  minute 
depression,  the  fovea  aentraiU.  The  "?tina  in  this  part  is 
very  thin,  and  the  sense  of  vision  is  most  perfect.  About 
one-tenth  of  an  inch  to  the  inner  side  of  this  spot  is  seen 
the  entrance  of  the  optic  nerve  ;  here  the  power  of  vision  is 
entirely  absent. 

Tlvi  retina  is  comr  >sed  of  three  principal  layers,  together 
with  blood-vessels  and  delicate  areolar  tissue  ;  the  external 
or  columnar ;  the  v.kldle  or  grantdar ;  and  the  internal  or 
nsrvods  layer;  each  of  these  is  again  subdivided  into  sub- 
layers, as  shown  in  Fig.  114. 

The  external  or  columnar  layer  is  exceedingly  tiiin,  and 
consists  of  solid  columnar  rod-like  bodie..,  with  cones  filled 
with  fluid  interspersed  at  regular  intervals  (a,  b).  These 
are  se))arated  from  tlie  granular  layer  by  a  transparent  homo- 
geneous membrane,  the  niembraiKi  Umltans  externa,  '''he 
middle  or  granular  layer  is  transparent,  finely  fibrillated 
and  comprises  one-third  of  the  thickness  of  the  letina.  It 
consists  of  two  layers  of  rounded  nuclear  i)articles  (c,  e) 
separated  by  an  inter-granular  layer  (d).  The  external 
granular  layei*  is  the  thicker,  and  its  particles  are  glohidar, 


20 


348 


I  HE  SPECIAL  SENSES. 


c 
c 

t 
I 
h 


I*.. 


and  coMJioct(Ml  witli  tlic  rods  jind  coiios  by  fihres  passing 
throni^li  l,li(»  mcniln'jina  li  mi  tans.  'V\w  intoi'nal  ^lannlar  layor 
' '"^  '"*  is  tli(^  tliinM(M',  and  its  pnrticlos  arc  flat- 

tened, looking  lil<(!  pieces  o['  money  seon 
edir(<ways,  lienco  called  tlio  immviular 
layei-.  Tlu'st>  colls  arc,  liowovef,  hipohir 
sendin{^  oiu)  process  ontwarils  tliidnj^h 
the  inter-grannlar  layer,  and  another  in- 
waids  through  the  molecular  layer,  to 
r(>ach  tlio  expansion  of  the  oi)tic  ncrvo. 
The  Internal  or  nervous  layer  is  thin, 
semi-tianspai'ent  and  consists  essentially 
ol'  the  expansion  of  the  terminal  fibres 
of  the  optic  nerve,  and  nerve  cells,  it 
also  ))resents  three  layers  ;  the  nwleeular 
or  linely  granular  layer,  resembling 
the  mol(>cular  matter  found  in  the  gray 
substance*  of  the  brain  and  spinal  cortl  ; 
tho  layer  of  ganglion  cells  or  nlhilar 
Vertioai  siHtioii  .'f  iii«   hwer,    whicli    consists    of     multipolar 

hiiniiin  ivtiiiik.     a,  Uods;  1'.  ,,  ^     ,  •       i   •    i 

••Olios.    ivtiiiK    upon  till!  cells,  some  oi  the  processes  of  which  pass 

niomliranii  liiiiitims  I'Xtoniii; 

.-,  cxtoiiiai  uiaiuiiar  la.Mi-;   (»ut\vard    t(^    the    uiolccular    layer    and 

d,    inli'iyi-.innliir   hixiT  ;   i",  _  ^  '' 

intorna)  miuiuiar  liiMi;  t.    others    inwards    to    the    fibrous    layer; 

■loU'Uilav  lav  or  ;  jr.  la\Of  of  _  .  ', 

«:aii-iion  >oiis ;  ii.iM>aii>ioii   .^,,,1  ^hc  fibroLis  layer  or  expansion  of  ( lie 

of  the  optu- noi-M-  libios  :  i,  -^  •'  ' 

mcmbranalimitttiis  interna.     optlC     ncrVC.       The    ncrVC    fibres     of   tluS 

l.iyer  consist  only  ol'  the  axis  cylinder,  and  some  of  them 
become  contiiuu)ns  with  the  })rolongations  of  the  ganglictn 
cells.  Tho  inner  surface  of  tho  retina  is  lined  by  a  trans- 
parent homogeneous  membrane,  which  separates  it  tfom  the 
vitreous  body,  the  mend)ra)Hi  liwifans  interna.  Blood- 
vessels are  only  found  in  the  internal  layer,  and  extending 
to  the  internal  granular  stratum  of  the  middle  layer.  In  tho 
external  or  rod-and-cone  layer  of  birds,  the  cones  predomi- 
nate, while  in  man  tho  rods  are  more  numerous.  In  noctur- 
nal animals,  tis  the  owl,  bat,  mole,  etc.,  the  cones  are  entirely 
absent.     In  the  fovea  centralis,  where  vision  is  most  acute> 


SENSE  OF  SIGl^T. 


349 


all  tlio  layiM'H  of  tlio  retina  am  tliiiincr  except  the  rods  and 
cones  which  are  increased,  from  vvhicli  it  wonld  apjx-ar  that 
these   are    more   especially   concerned    in    tlie  fnrkction  of 


vision. 


The  ((([iieoufi  humor  occupies  the  anteiior  part  of  the 
giohe,  and  coniph^tely  fills  the  anterior  and  posterior  cham- 
bers of  the  eye.  It  is  a  clear,  thin  fluid,  havin*^  an  alkaline 
reaction,  which  is  due  to  the  presence  of  chloride  of  sodium. 
In  the  adult,  the  anterior  and  posterior  chambers  communi- 
cate through  the  pupil ;  hut  in  the  foetus,  before  the  seventh 
month,  the  pupil  is  closed  by  the  meml)rana  pupillaris.  The 
persistence  of  this  membrane  sometimes  occasions  congeni- 
tal blindness. 

The  viireouN  liamor  occupies  the  posterior  fbur-til"ths  of 
the  globe.  It  is  perfectly  trai'.sparent,  of  the  consistence  of 
jelly,  aiul  consists  of  numerous  layers  of  sim|)le  membiano 
with  the  intervening  spaces  filled  with  fluid.  It  is  sur- 
rounded by  the  hyaloid  membrane,  and  is  hollowed  out  in 
front  for  the  reception  of  the  crystalline  lens.  It  refracts 
tho  rays  of  light,  and  fills  the  globe  of  tiie  eye  so  as  to  keep 
the  retina  at  a  [)i'o|)er  distance  from  tin;  lens.  The  vitreous 
humor  contains  some  salts  and  a  litth;  albumen.  In  the 
foetus,  a  minute  artery  passes  through  the  centre  to  the  pos- 
terior part  of  the  capsule  of  the  lens,  the  arteria  centralis 
retliicv ;  but  it  di,sa[)pears  in  the  adult. 

The  crystalline  ^c/t.s,  enclosed  in  its  capsule,  is  situated  in 
front  of  the  vitreous  humor  and  behind  the  pupil.  The  aip- 
Hule  is  a  transparent  brittle  membiane,  highly  elastic,  and 
is  dis})o.si!d  to  curl  inwards  upon  itself  when  ruptured.  It 
surrounds  the  lens,  to  which  it  is  connected  by  a  layer  of 
nucleated  cells,  and  is  held  in  position  by  the  HaHpensori/ 
ligament,  which  connects  it  to  the  anterior  margin  of  the 
retina.  The  suspense  .y  ligament  consists  of  two  layers 
blended  together;  the  outer,  a  milky,  granular  layer,  cornea 
in  contact  with  the  inner  surface  of  the  ciliary  processes  ; 
the  inner,  is  an  elastic  transparent  membrane.     This  liga- 


^p 


350 


THE  SPECIAL  SENSES. 


c 
t 

Ml 
t 

L 
h 

•J 

in 


i 


mcnt  forms  part  of  the  boundary  of  the  posterior  cliainber 
of  tlie  eye  ;  its  posterior  surface  is  separated  from  .e  hya- 
loid membrane  by  a  triangular  interval — the  canal  of  Petit. 
This  canal  is  about  one-tenth  of  an  inch  wide,  bounded  in 
front  by  the  suspensory  ligament,  behind  by  the  hj^aloid 
membrane,  and  the  base  is  foi'ined  by  the  capsule  of  the 
lens. 

The  lens  itself  is  a  transparent  double  convex  body, 
being  more  convex  behind  than  in  front.  It  measures  about 
four  lines  transversely  and  three  lines  from  before  back- 
wards. It  appears  to  consist  of  concentric  laminae,  like  the 
coats  of  an  onion,  the  central  ones  forming  a  hardeneo  nu- 
cleus. It  also  ap))eai\s  to  consist  of  three  triangular  seg- 
ments ;  this  is  readily  demonstrated  by  boiling,  or  immersing 
it  in  alcohol.  The  lamina?  consist  of  minute  parallel 
fibres,  hexagonal  in  shape,  the  edges  being  dentated  and 
fitting  into  each  other,  and  are  about  saoo  of  an  inch 
(5  mnmi.),  in  diameter.  The  refi'acting  media  of  the  eye  are 
the  cornea,  aqueous  humor,  crystalline  lens,and  the  vitreous 
humor. 

There  are  two  forms  of  the  lens  in  the  human  eye,  viz., 
the  concavo-convex  or  7}ieniscus,  as  the  cornea ;  and  the 
double  convex,  as  the  crystalline  lens.  The  essential  parts 
of  the  eye,  appear  to  be  :  1st,  a  dark  coat  to  absorb  the 
rays  of  light — the  choroid  ;  2nd,  a  nervous  expansion  to  re- 
ceive and  transmit  to  the  brain  the  impression  of  light — 
the  retina ;  3rd,  a  concavo-convex  lens  to  collect  the  rays 
of  light  from  the  object  and  direct  them  inwards,  and  a 
double  convex  lens  to  collect  the  rayt.  of  light  and  bring 
them  to  a  focus,  so  as  to  form  a  correct  image  on  the  retina 
— the  cornea  and  the  lens ;  4tn,  a  contractile  cui'tain  with 
a  central  opening,  to  regulate  the  quantity  of  light  enter- 
ing the  eye — the  iris.  The  eye  is  thus  a  simple  o])tical  in- 
strument, endowed  with  vitality,  and  acting  as  required 
without  assistance.  It  is  abundantly  supplied  with 
blood-vessels.    In  addition  to  the  conjunctival  vessels,  there 


PHENOMENA  OP   VISION. 


351 


cli  amber 
-d  hya- 
of  Petit 
inded  in 
hj-aloid 
e  of  the 

f^x  body, 
es  about 
•e  back- 
like the 
!ned  nu- 
lar  .seer- 
mersing 
parallel 
ted  and 
an  inch 
eye  are 
vitreous 

ye,  viz., 
a-nd  the 
a,l  parts 
iorb  the 
n  to  re- 
light— 
he  rays 
s,  and  a 
I  bring 
3  retina 
in  with 
^  enter- 
ical  in- 
3quircd 
i    with 
3,  there 


are  the  vessels  of  the  sclerotic,  choroid,  iris  and  retina. 
The  latter  are  derived  from  the  short,  long,  and  anterior 
ciliary  arteries,  and  the  arteria  centralis  retinae. 

Phenomena  of  Vision. — In  order  fully  to  understand 
the  physiology  of  vision,  it  will  be  necessary  to  refer  briefly 
to  some  of  the  laws  which  regulate  the  transmission  of 
light. 

1st, — Light  travels  in  parallel  rays  through  a  medium  of 
uniform  density. 

2nd, — When  the  rays  meet  with  a  medium  of  increased 
density,  they  become  refracted,  or  changed  in  direction,  to- 
wards a  line  which  falls  perpendicularly  to  the  surface  of 
the  body  which  they  enter. 

3rd, — When  the  rays  of  light  meet  with  a  medium  of 
diminished  density,  they  are  refracted  from  the  perpendicu- 
lar line. 

4th, — When  the  rays  of  light  fall  upon  a  convex  lens, 
they  are  collected ;  and  if  this  be  a  double  convex  body, 
they  come  to  a  point  or  focus  at  a  certain  distance,  de- 
pending on  the  degree  of  convexity  of  the  lens  ;  the 
greater  the  convexity  the  shorter  the  distance  and,  vice 
versa.  The  image  formed  by  thj  refraction  of  the  rays  of 
light  in  coming  to  a  point  or  focus  will  be  an  inverted  one. 

5th, — If  the  convexity  of  the  lens  be  too  great,  the  focus 
will  be  formed  in  front  of  the  mirror  or  reflecting  body. 
If  too  slight,  the  focus  will  be  formed  beyond  it. 

Vision  is  accomplished  by  the  formation  of  an  image  of 
the  object  looked  upon,  on  the  internal  surface  of  the  retina. 
The  impression  made  upon  this  produces  a  sensation,  which 
is  conveyed  to  the  sensorium  by  the  optic  nerve,  and  the 
mind  takes  cognizance  of  it. 

The  image  is  formed  in  the  following  manner : — The 
rays  of  light  are  reflected  from  the  object  (A.  B.),  and  im- 
pinge on  the  outer  convex  surface  of  the  cornea  (c.  c), 
through  which  they  pass,  becoming  refracted  towards  the 
perpendicuk,r.     Those  which  fall  on  the  circumference  of 


352 


THE  SPECIAL  SENSES. 


the  corn(;a  impinge  upon  the  iris,  and  are  reflected,  show- 
ing the  color  of  this  structure;  those  which  pass  nearer  its 


Fi'T.  115. 


c 

Ik 

t 

L 
h 

m 

■v 

I 
IB) 

F 

lar> 
•»»      . 

«n 


centre,  converge  and  enter  the  pupil.  They  now  penetrate 
the  crystalline  lens  (e.  e.),  by  means  of  v/hich  they  are  still 
further  converged,  their  convergence  ^^jijig  completed  by 
their  passage  through  the  vitreous  humor,  and  are  brought 
to  a  focus  on  the  inner  surface  of  the  retina  (a.  and  b.).  If 
the  retina  be  not  at  f.,  but  at  g.  or  h.,  certain  luminous 
spots,  e  and  o,  or  c  and  f,  will  be  seen ;  for  at  n  the  rays 
have  not  yet  met,  and  at  G  thej''  have  crossed  and  are  again 
diverging.  Since  rays  of  light  come  from  all  points  of  the 
object,  and  are  refracted  in  their  passage,  they  must  cross 
each  other,  and  thus  the  image  of  the  object  on  the  retina 
(f),  will  be  inverted,  but  this  is  corrected  by  the  sensorium. 
The  angle  of  crossing  is  called  the  visual  angle. 

Accommodation  of  the  Eye  to  Vision. — It  is  quite  evi- 
dent that  some  arrangement  of  the  refractive  parts  of  the 
eye  is  necessary  to  adapt  it  to  the  vision  of  near  and  distant 
objects.  The  precise  manner  in  which  this  accommodation 
is  effected  is  a  disputed  point ;  some  maintain  that  it  is  due 
to  an  alteration  in  the  position  of  the  lens  ;  while  others 
regard  it  as  being  due  both  to  an  alteration  in  the  position 
and  shape  of  the  lens.  The  eye,  in  its  normal  state,  is 
accommodated  for  distant  vision,  under  the  guidance  of  the 
recti  muscles  ;  this  may  be  called  its  passive  condition.    The 


ACCOMMODATION  OF  THE  EYE  TO  VISION.     353 


;•!,  sbow- 
U'arcr  its 


Denetrate 
'  are  still 
ileted  by 
brought 
lb.).  If 
luminous 
the  rays 
are  again 
its  of  the 
ust  cross 
lie  retina 
nsorium. 

luite  evi- 
ts  of  the 
\  distant 
nodation 
it  is  due 
e  others 
position 
state,  is 
CO  of  the 
on.    The 


active  accommodation  of  the  eye  for  the  vision  of  near  ob- 
jects is  caused  by  the  advance  of  the  crystalline  lens  towards 
the  cornea,  and  also  by  the  increased  convexity  of  its  ante- 
rior surface.  It  is  advanced  towards  the  cornea  chiefly  by 
»  ^  .  action  of  the  ciliary  muscle,  and  partly  by  the  compres- 
sion exercised  upon  the  posterior  three-fourths  of  the  eye- 
ball by  the  recti  muscles.  It  may  therefore  be  inferred  that 
the  recti  muscles  adapt  and  adjust  the  eye  for  ordinary 
vision ;  while  the  ciliary  muscle  may  be  regarded  as  the 
Ane  adjuster,  which  regulates  the  eye  for  the  vision  of  near 
or  very  small  objects. 

The  rays  of  light  which  pass  through  the  margin  of  a 
lens  are  more  refracted  than  those  which  pass  through  the 
centre,  and  owing  to  this  unequal  refraction  the  rays  do  not 
all  meet  at  the  same  point.  This  defect  is  called  spherical 
aberration.  The  formation  of  distinct  and  correct  images 
on  the  retina  is  favoured  by  the  action  of  the  pupil,  which 
prevents  the  rays  of  light  from  passing  through  any  part  of 
the  lens  but  its  centre,  and  thus  preventing  any  tendency  to 
spherical  aberration.  In  optical  insti  uments,  as  the  micro- 
scope, telescope,  etc.,  spherical  aberration  is  prevented  by 
the  use  of  a  diaphragm  with  a  circular  aperture,  which 
shuts  out  all  the  marginal  rays.  Distinctness  of  vision  is 
further  secured  by  the  black  coating  of  pigment  on  the 
inner  surface  of  the  choroid,  which  absorbs  any  rays  of 
light  which  may  be  reflected  within  the  eye,  and  prevents 
them  from  being  thrown  back  again  upon  the  retina,  so  as 
to  produce  dazzling  of  the  image  there  formed. 

When  a  ray  of  light  passes  through  an  ordinary  lens  it  is 
partly  decomposed  into  its  elementary  colors,  and  a  colored 
margin  appears  around  the  image  owing  to  the  unequal  re- 
fraction of  the  elementary  colors.  This  is  called  chromatic 
aberration,  and  is  corrected  in  optical  instruments  by  the 
combination  of  two  or  more  lenses,  differing  in  shape  and 
density.  The  combination  usually  consists  of  two  lenses  of 
unequal  refraction,  a  convex  lens  made  of  crown  glass  and 


354 


THE  SPECIAL  SENSES. 


c 

c. 

t 

L 

I 

r 


and  a  concave  one  of  flint  glass,  but  the  number  may  be 
varied  to  suit  the  circu instances.  Such  combinations  of 
lenses  are  called  achromatic.  The  unequal  refractive  powers 
of  the  different  media  of  the  eye  prevent  chromatic  aber- 
ration. If  a  ray  of  white  light  be  passsed  through  a  prism 
the  different  colors  are  refracted  in  different  degrees,  and  a 
colored  band  appears,  called  the  spectrum,  arranged  as  fol- 
lows :  violet,  indigo,  blue,  green,  yelloiu,  orange  and  red. 
The  violet  rays  are  most  refrangible ;  the  red  the  least ; 
hence  the  image  of  a  small  white  object  appears  as  if  sur- 
rounded with  a  yellowish  or  bluish  fringe,  because  it  cannot 
be  accurately  focused  on  the  retina,  This  is  called  irra- 
diation. For  this  reason  a  white  figure  on  a  black  ground 
appears  larger  than  a  black  one  of  the  same  size  on  a  white 
ground. 

The  inverted  image  of  any  bright  object,  as  the  windows 
of  the  room  may  be  distinctly  seen  in  the  eye  of  any 
albino  animal,  as  a  white  rabbit ;  or  if  an  opening 
be  made  at  the  superior  surface  of  the  eye  so  that  the 
retina  can  be  seen  through  the  vitreous  humor,  a  reversed 
image  of  any  bright  object  may  be  seen  on  the  posterior 
wall  of  the  eye.  Impressions  once  produced  on  the  retina 
remain  for  a  short  iime  afterwards;  their  duration  depending 
on  the  intensity  of  the  impression  they  have  left.  A  moment- 
ary impression  of  moderate  intensity  continues  about  one- 
eighth  of  a  second.  This  is  the  reason  why  the  act  of  wink- 
ing does  not  interfere  with  the  continuous  vision  of  surround- 
ing objects.  The  spectra  which  remain  on  the  retina  after 
viewing  colored  objects  are  always  of  the  opposite  or  com- 
plemental  color ;  e.  g,  the  spectrum  of  a  red  object  is  green, 
that  of  violet,  yellow,  etc.  This  is  because  the  retina  be- 
comes fatigued  by  the  color  looked  at ;  but  remains  sensitive 
to  the  other  rays. 

There  is  in  front  of  the  eye  a  certain  space  within  which 
objects  are  perceived,  and  beyond  which  nothing  can  be 
distinctly  seen  ;  this  is  called  the  circle  or  Jleld  of  vision 


THE  BLIND  SPOT. 


355 


and  varies  in  extent  in  different  circumstances.  For  ex- 
ample, if  the  eye  is  intently  fixed  upon  one  word  in  the 
middle  of  the  page,  this  word  and  those  that  immediately 
surround  it,  which  are  in  the  circle  of  vision,  are  distinctly 
visible,  while  those  at  the  circumference  are  imperceptible 
while  the  eye  remains  fixed.  It  is  largest  when  the  view  is 
not  confined  to  any  near  object. 

The  distinctness  with  which  an  object  may  be  seen, 
appears  to  depend  largely  upon  the  number  of  rods  and  cones 
covered  by  the  retinal  image,  hence,  the  nearer  an  object  is 
to  the  vision  of  the  eye,  the  more  distinctly  are  its  details 
seen.  The  images  of  two  points  require  to  be  at  least 
T7^ot)  of  an  inch  (2  mmm)  apart,  in  order  to  be  distinguished 
separately.  That  portion  of  the  retina  which  corresponds 
to  the  entrance  of  the  optic  nerve  is  insensible  to  light,  and 
is  called  the  blind  spot.  It  we  close  the  left  eye,  and  direct 
the  right  steadily  upon  the  circular  spot  here  shown,  while 

•  + 

the  page  is  about  six  inches  from  the  eye,  both  marks  are 
visible.  If  the  distance  be  gradually  increased,  the  cross 
disappears  from  view,  and  if  the  book  be  still  further  re- 
moved, it  comes  in  sight  again. 

The  eye,  in  the  uneducated  state,  cannot  comprehend 
the  properties  of  the  objects  seen,  as  color,  form,  etc., 
or  the  distance  of  the  object;  this  is  acquired  by  experience. 

Simultaneous  Action  of  the  two  Eyes. — Although  an 
imageof  the  object  is  formed  oneach  retina,  yet  tlie  impression 
of  the  object  conveyed  to  the  mind  is  single.  This  is,  no  doubt 
owing  to  the  fact  that  the  image  is  formed  on  identical 
points  of  both  retinae,  giving  rise  to  but  one  sensation,  and 
the  perception  of  a  single  image — the  result  of  a  mental  act. 
This  unity  of  action  may  be  favoured  by  the  continuation 
of  the  optic  filaments  across  the  anterior  part  of  the  chiasma 
of  the  optic  nerve,  but  is  not  dependent  on  it ;  for,  if  the 
visual  axis  of  one  eye   be  altered,  objects  are  seen  double. 


35G 


THE  SPECIAL  SENSES. 


c 

11 


K 


r 


This  may  be  demonstrated  by  pressing  the  eyeball  on  one 
side  with  the  finger  in  order  to  rotate  it  upon  its  axis,  while 
the  eyes  are  fixed  upon  some  object,  as  a  book  or  lamp ;  two 
images  of  the  object  are  seen  as  in  diplopia  from  strabismus. 
This  is  owing  to  the  formation  of  images  of  the  objects  on 
different  parts  of  the  two  retinae.  The  power 'of  combining 
tlie  two  images  is  subservient  to  the  faculty  of  obtaining  a 
j)roper  conception  of  bodies  raised  in  relief.  When  a  solid 
object  as  a  cube  is  viewed,  a  different  perspective  of  it  is 
seen  by  each  eye,  and  more  of  the  surface  of  the  body  is 
seen  than  if  viewed  with  one  eye  ;  in  other  words  a  stereo- 
scopic effect  is  produced. 

Defects  of  Vision. — The  normal,  or  emmeto^opic  eye 
brings  parallel  rays  of  light  exactly  to  a  focus  on  the  retina 
(Fig.  IIG,  i)  and  all  objects  except  near  ones  (within  20  feet), 
are  seen  without  any  effort  of  accommodation.  In  looking 
at  near  objects  the  eye  is  accommodated  by  the  action  of 
the  ciliary  muscle,  and  the  rays  which  would  otherwise  meet 
behind  the  retina  are  correctly  focused  upon  it,  (Fig.  116,  2, 
dotted  lines).  The  defects  of  vision  are  myopia,  hyperme- 
tropia,  presbyopia  and  astigmatism. 

Myopia  is  due  to  an  abnormal  elongation  of  the  eye  ball, 
and  too  great  a  degree  of  convexity  of  the  lens.  The  rays  of 
light  are  brought  to  a  focus  in  front  of  the  retina,  and  the 
images  are  indistinct  and  blurred  (Fig.  IIG,  4).  The  eye  is 
naturally  accommodated  for  a  near  point,  and  objects  near 
the  eye  are  exactly  focused,  while  those  beyond  the  .%r  point 
cannot  be  distinctly  seen.  This  defect  is  remedied  by  wear- 
ing concave  glasses.  On  the  other  hand,  when  the  eye  is  short, 
and  the  lens  flat,  parallel  rays  are  focused  behind  the  retina; 
the  eye  is  naturally  accommodated  for  distant  objects  (Fig. 
11 G,  3).  This  is  called  hyperm^etropia,  and  may  be  remedied 
by  wearing  convex  glasses  which  converge  the  rays  of  light 
Presbyopia  is  an  ervor  of  refraction,  and  must  not  be  con- 
founded with  hypermetropia.  It  is  the  gradual  loss  of  the 
power  of  accommodation  which  occurs  with  advanced  age, 


DEFECTS  OF  VISION. 


357 


1  on  one 
^; is,  while 
»np;  two 
abismus. 
bjects  on 

)nibinin£r 
:aining  a 
n  a  solid 
of  it  is 
body  is 
a  stereo- 

>pic  eye 
le  retina 
20  feet), 
looking 
iction  of 
ise  meet 
.  116,  2, 
i/perme- 

ye  ball, 
!  rays  of 
md  the 
e  eye  is 
ts  near 
ir  point 
Y  wear- 
issliort, 
retina; 
:s  (Fig. 
nedied 
f  light 
)e  con- 
of  the 
d  age, 


and  is  likevvi.se  remedied  by  the  use  of  convex  glasses.  As- 
ti(/ mat  187)1,  first  discovered  by  Airy,  is  due  to  a  greater  cur- 
vature of  the  eye  in  one  ])lane  than  in  another,  so  that 
vertical  and  horizontal  lines  crossing:  each  other  cannot  be 

l-'i^'.    lUi. 


focused  at  the  same  point,  and  the  images  are  blurred  and 
indistinct.  It  may  be  remedied  by  using  glasses  curved 
only  in  one  direction — cylindrical  glasses. 

Daltonism,  or  color  blindness,  is  also  a  defect  of  frequent 
cocurrence  ;  many  persons  are  wholly  unable  to  distinguish 
between  red,  green  and  yellow.  This  would  appear  to  arise 
from  some  defect  in  those  elements  of  the  retina  which  re- 
ceive the  impressions  of  these  colors. 


^m 


358 


IT///-:  S/'EC/A/.  SENSES. 


HEARING. 

The  ear  is  the  orgun  of  hearing,  and  is  composed  of  three 
l)ortions,  the  external,  middle  and  internal  oar. 

The  external  ear  consists  of  an  expanded  portion,  the 
pinna,  the  meatus  auditoriua  txternus,  and  auditory  canal. 
Its  use  is  to  collect  the  vibrations  of  the  air,  and  conduct 
them  to  the  membrana  tympani,  or  drum,  which  separates 
the  external  from  the  middle  ear.  The  canal  contains  some 
fine  hairs  at  its  outer  part,  and  also  a  number  of  sebaceous 
glands  throughout  its  whole  extent,  which  secrete  a  waxy- 
substance  termed  cerumen. 

Fijf.  117. 


O,  Pinna  ;  b,  external  auditory  passage  ;  c,  membrana  tympani  (section) ;  d,  insertion  of 
membrana  tympani  in  bony  canal ;  e,  insertion  of  malleus  in  membrana  tympani ;/,  base  of 
stapes,  inserted  in  the  fenestra  ovalis  ;  g,  incus,  joining  stapes  and  malleus,  and  complet- 
ing the  chain  of  ossicles  ;  h,  cavity  of  the  tympanum  ;  (',  Eustachian  opening  of  tym- 
panum ;  j,  opening  of  Eustachian  tube  in  the  pharynx  ;  k,  posterior  part  of  pharynx;  I, 
semicircular  canals  ;  tii,  n,  cochlea  ;  u,  trunk  of  auditory  nerve. 

The  middle  ear  or  tj/m'panum  is  situated  in  the  petrous 
portion  of  the  temporal  bone,  between  the  membrana  tym- 
pani externally,  and  the  internal  ear  or  labyrinth  in- 
ternally.    It  is  filled  with  air,  and  communicates  with  the 


.s7;a;s/-;  r/  hearing. 


So) 


of  three 

ion,  the 
y  canal. 
conduct 
eparates 
ns  some 
baceous 
a  waxy 


isertion  of 
i;/,  base  of 
1  complet- 
jf  of  tym- 
larynx;  I, 


)etrous 
a  tym- 
th  in- 
th  the 


l)liarynx  thi-on^jli  tho  Eustacliiaii  tiibt',  wliich  opens  at  tho 
back  part  of  t Ik;  iniorior  meal.ns,  (Fin;  iHj.  Tt  als(*  com- 
municates postei'iorly  with  ;iir  cuvitios  in  iln-  mastoid 
process  of  the  temporal  bone,  the;  'laasfoid  celh.  It  is 
crossed  by  a  chain  of  movable  bones,  which  receive  the 
impressions    from    the   memlirana   t3'mpaiii,   and   serve  to 


FL'.  1 18. 


Interior  of  til  0  osseous  lain  liiitii.  V.  \u.'5tiliulo,  <ii\  A(|Uodiu;t  of  tlie  vcstilmle.  n. 
Fovea  heiiiielliptica.  r.  Fovea  huinisjiherica.  S.  SeniiciriMilar  lauals.  n.  Superior,  jt. 
Posterior,  i.  Inferior.  (t,a,(i.  The  anii)ullar  extremity  nf  eacli.  f.  Cuililea.  ac.  A()iic(luef 
of  the  cochlea,  sv.  Osseous  zone  of  the  lamina  spirali-;,  above  wliieh  is  the  scala  vestibuh, 
conimunicatin!,'  with  the  vestibule,     nt.  Scala  tynipaui  below  the  spiral  lamina, 

transmit  them  to  the  internal  ear,  upon  whieli  the  auditory 
nerve  is  distributed.  The  bones  of  the  ear  are  the  malleus, 
incus,  and  stajoes ;  the  handle  of  the  malleus  is  received 
between  the  inner  and  middle  layers  of  the  membrana 
tym})ani,  and  the  stapes  is  implanted  in  the  fenestra  ovalis. 
The  cavity  of  the  tympanum  and  its  chain  of  bones  are 
lined  with  mucous  membrane,  continuous  with  the  i)harynx 
through  the  Eustachian  tube,  and  covered  with  ciliated 
epithelium. 

The  internal  ear  or  labyrinth,  is  the   essential  part  of 
the  organ  of  hearing,   and  consists  of  the  vestibule,  semi- 


360 


THE  SPECIAL  SENSES. 


c 
t 


•••ii; 


circular  canals,  and  cochlea.  It  consists  of  a  series  of 
cavities  liolluvved  out  of  the  petrous  portion  of  the  tem- 
poral hone,  couinuini'jatinf,'  externally  with  the  middle  ear 
throu^di  the  fenestra  ovalis  and  fenestra  lotunda,  and 
internally  with  the  cranial  cavity  through  the  meatus 
auditorius  interims,  which  transmits  tlni  auditory  nerve. 
The  vcsfUmIe  is  the  central  organ  and  middh;  cavity  of 
the  labyrinth.  In  its  inner  wall  are  several  o})t'nings  for 
the  entrance  of  the  branches  of  the  auditory  nerve  ;  in  its 
outer  wall  is  the  opening  of  the  fenestra  ovalis  which  re- 
ceives th(!  stapes  ;  in  its  posterior  and  superior  walls  are  the 
openings,  five  in  number,  of  thesemiciicuhir  canals  ;  and  in 
its  anterior  wall  the  opening  into  the  cochlea.  The  semicir- 
cular canals  are  three  arched  bony  canals  which  opei'  at 
both  ends  into  the  vestibule,  two  of  them  Hrst  coalescing. 
One  end  of  each,  more  dilated  than  the  other,  is  called  the 
ampulla. 

The  cochlea  is  situated  in  front  of  the  vestibule,  and 
is  shaped  like  a  snail  shell.  Its  axis  presents  a  conical 
column,  the  modiolus,  arouiid  which  winds  a  spiral  canal, 
raakinr;  about  two  and  a  half  turns  fi'om  the  ba.se  to  the 
apex.  At  the  base  there  are  three  openings,  the  vestibular 
opening,  the  fenestra  rotunda  and  the  aqtuvductus  cocJdea. 
The  spiral  canal  is  divided  into  passages  or  scahie,  by  the 
lamina  spiralis  os.sea which  consists  of  two  lamiiue  of  bone 
between  which  arc  canals  for  the  entrance  of  the  nervus 
cochlearis.  One  of  those  passages  communicate.^  with  the 
yestihu]c,  the  scalavestibull;  the  other  with  the  tympanum, 
the  scala  ti/mpanl.  Between  these  is  a  third  space  called 
the  scala  medla,ov  canalis  cochlene  (Fig.  119,  cc )  The  lamina 
spiralis  ends  at  the  apex  of  the  cochlea  in  a  small  hamulus, 
the  inner  and  concave  surface  of  which,  when  separated 
from  the  modiolus  leaves  a  small  aperture,  the  hellcotrema 
through  which  the  scalse,  sei)arated  in  the  rest  of  their  ex- 
tent, communicate.     The  lamina  spiralis  ossea  extends  only 


SENSE  OF  HEARING, 


361 


serios   of 
the  tem- 
i<ldlo  ear 
i<la,    and 
meatus 
y  nerve, 
3avity  of 
iiing.s  for 
e  ;  in  its 
liich  re- 
H  arc  the 
;  and  in 
!^cmicir- 
opei'  at 
ilescing. 
Ucd  the 

^ile,  and 

conical 

I  canal, 

to  the 
tihular 
cochlea. 
by  the 
»f  bone 
nervus 
ith  the 
)anum, 

called 
lamina 
niulus, 
arated 
^trema 
iir  ex- 
s  only 


part  of  the  distance  between  the  niodioln.s  and  the  outer 
wall  of  the  cochlea,  and  swells  up  at  the  outei  end,  forming 
the  limbus  lamlnoi  spiralis,  the  i)order  of  which  is  grooved, 
the     sulcus      spiralis.  •■■'»•  ii''- 

From  the  inferior  mar- 
gin of  this  groove 
a  membrane  stretches 
across  to  the  bony  wall 
of  the  cochlea  complet- 
ing the  lamina  spiralis, 
called  the  memhrana 
haailaris,  the  outer 
attachment  of  which 
forms  a  thick  triangu- 
lar structure  the  li(ja- 
vnentum  spirale.  From 

f>iA  ni->r.or  niovfrin  f\f  lamiiiii!  spirulis ;  .v.s,  sulcus -|  inili.s  ;  .'/x,  H;an},'lioinpir!klo 
tne     Upptl      maigin      OI    seatoa  on  «(!,  tUo  nu.vus  ouohloaiis,  itidiuitcit  l.y  tho 

flio         01/7/11.U        o.iQi.//7i"u  '^''^"''   """•  '""•  'a""'"'  spiralis*   <)s^ea  ; /,  uniuibruiia 

tiie         .•>  t«/(/0  ct/.5        Hffll  K/Vm  tectoriaof  Corti  ;  b,  ineinlirana  liasilaris  ;  Cn,  or;,'un  of 

i.  .    i    1  ,1  Corti  : /;(i),  li!,'iiiJiurituni    spirale:   1,    inturiial    i'(k1    of 

stretches  across  another  Corti;  2,  external  .0.1  of  CorU. 


Section  tlirouj^li  one  of  tlie(  oilsof  tlic  cochlea  ht, 
seala  tynipani ;  »v,  scala  vcstiliuli  ;  cc,  s.iala  media  or 
canalis  coclileaj  ;  u,  nicnil)ranc  of  Hcissuer,  witli  itti 
sinirle  layer  of   nucleated    flattened  cells  ;   lis,  liinhu.s 


Corti, 

Fur- 

7nem- 

forms 


membrane  which  covers  over  the  organ  of 
the  memhrana  tectoria,  or  membrane  of  Corti. 
ther  inwards  is  another  thin  membrane,  the 
brane  of  lieissner,  which  stretches  across  and 
the  scala  media,  or  canalis  Goohlea}.  The  organ  of  Corti 
is  situated  upon  the  membrana  liasilaris.  It  consists  of 
the  rods  of  Corti,  arranged  in  a  series  of  arches  formed  by 
the  internal  and  external  rods  roofing  over  the  zona  arcu- 
ata  (Fig.  119.  i,  2.).  They  incline  inwards  towaids  each 
other,  and  each  ends  in  a  swelling  termed  the  head,  the  con- 
vexity of  one  fitting  into  the  concavit}--  of  the  other  like  an 
articulation.  It  has  been  estimated  that  there  are  about 
3000  of  these  pairs  of  rods  or  pillars  from  the  base  to  the 
apex  of  the  cochlea.  On  both  sides  of  these  rods  are  cylin- 
drical epithelial  cells,  some  of  which  are  provided  with 
cilia  (cells  of  Corti.) 

Within  the  osseous  labyrinth  is  contained  the  membran-- 


■mp 


362 


IHE  SPECIAL  SENSES. 


c 

L 

mi 
I 


OILS  labyrinth,  upon  wliicli  is  distributed  the  tiliinicuts  of  the 
auditory  nerve.  Tlie  nieinbrauous  labyrinth  is  lilled  with 
a  transparent  lluid,  called  cndolynipli  ;  while  between  it 
and  tlie  osseous  covering  is  a  lluid  called  peril i/viph,  so  that 
tlie  sonorous  vibrations  which  reach  the  auditoiy  neive  in 
these  parts  arc  conducted  through  lluid,  to  a  membrane  con- 
taining fluid.  In  the  vestibular  })ortion  of"  the  mend)ranous 
hibyrinl.h  arc  two  cavities;  the  upper  and  larger  is  named 
he  uti'iciiliifiyiind  the  lower  the  saccnlus.  They  are  situ- 
ated respectively  in  the  fovea  hon'ielliptica  and  the  foveti 
hemiKphevlcd  and  contain  small  masses  of  calcareous  matter, 
the  oioliths  (Fig.  ll.S).  The  utricle  connnunicates  with  the 
membranous  semiciicular  canals  and  the  saccule  with  the 
canalis  cochlear 

The  iMr.rnANiSM  of  ITk.vuino. — The  ((KdUori/ nerve  as  it 
enters  tlio  ear  divides  into  two  branches,  one  to  the  vestibule 
and  the  amjmlhe  of  the  semicircular  canals,  and  the  other 
to  the  cochlea.  The  branches  of  the  cochlear  nerve  enter 
through  openings  at  the  base  of  the  modiolus,  and  pass  ijito 
canals  between  the  ))lates  of  the  lamina  spiralis,  in  which 
they  form  a  plexus  containing  ganglion  cells  (Fig.  110,  //n), 
and  terminate  in  the  oi-gan  of  Corti.  The  external  (>ar 
favors  the  proi>agation  of  sound  by  collecting  the  r.onorous 
undulations,  and  conducting  them  to  the  meml)rana  tym- 
pani,  and  also  by  the  resonance  of  the  column  of  aii'  con- 
tained in  the  auditory  canal.  The  elevations  and  depressions 
of  the  pinna  servo  a  useful  pui])o,se,  for  sonorous  umlulations 
from  whatever  direction  they  come,  must  fall  perpcndiculaily 
upon  the  tangent  of  some  one  of  them.  Sonorous  vibra- 
tions are  conducted  to  the  ear  by  three  different  media,  the 
air,  the  osfficlefi  of  the  car,  and  the  Jiuid  of  the  labyrinth. 
The  propagation  of  the  sounds  to  the  fluid,  is  made  more 
perfect  by  reason  of  the  ossicles  being  fixed  in  the  middle 
of  a  tense  vibrating  membrane,  with  air  on  both  sides, 
as  the  tympanum.  Sounds  are  collected  by  the  external 
ear  and  are  transmitted  to  the  membrana  tympani.     They 


THE  MECHANISM  OF  HEARING. 


363 


are  here  modified  by  the  tense  or  lax  state  of  this  mem- 
brane, produced  by  the  action  of  the  laxator  and  tensor 
tympani  muscles.  The  modified  vibrations  from  the  mem- 
brana  tympani  are  thence  conducted  along  the  chain  of 
bones  to  the  fluid  of  the  labyrinth,  and  through  it  trans- 
mitted to  the  auditory  nerve,  which  receives  the  impressions.' 
and  conveys  them  to  the  sensorium.  From  various  experi- 
ments which  have  been  performed,  it  appears  that  tension 
of  the  membrana  tympani  is  unfavorable  generally  to  the 
propagation  of  sounds,  especially  those  of  a  low  pitch. 
This  may  be  shown  by  making  a  continuous  eflfort  of  expir- 
ation or  of  inspiration,  while  the  mouth  and  nostrils  are 
closed  by  the  hand.  The  eftbrt  of  expiration  causes  the 
air  to  be  forced  into  the  tympanum  through  the  Eustachian 
tube,  the  membrana  tympani  is  made  to  bulge  out  and 
become  tensp,,  and  the  hearing  is  indistinct.  The  effort  of 
inspiration  exhausts  the  air  from  the  cavity  of  the  tym- 
panum, and  the  pressure  from  without  causes  the  membrana 
tympani  to  bulge  inwards  and  become  tense,  and  is  fol- 
lowed by  temporary  deafness. 

The  action  of  the  chain  of  bones,  as  conductors,  is  en- 
hanced by  the  presence  of  air  in  the  cavity  of  the  tympa- 
num. It  serves  to  isolate  the  bones  so  as  to  propagate  the 
vibrations  with  concentrated  intensity,  and  prevent  the 
dispersion  of  sound.  The  air  is  supplied  through  the  Eusta- 
chian tube,  which  communicates  with  the  pharynx  just  be- 
hind the  posterior  .ares.  When  persons  are  listening  very 
intently,  the  mouth  is  usually  partly  open,  in  order  to  allow 
a  free  current  of  air  to  pass  through  the  Eustachian  tube. 

The  semicircular  canals  collect  the  sonorous  undulations 
from  the  bones  of  the  cranium  and  conduct  them  to  the  ampullae 
and  utriculus,  where  the  auditory  nerve  is  distributed.  The 
cochlea  is  intended  for  the  spreading  out  of  the  nerve  fibres 
over  a  wide  extent  of  surface,  and  for  the  perception  of 
sounds  by  the  solid  parts  and  the  walls  of  the  labyrinth. 
The  membranous  labyrinth  of  the  vest     'le  and  semicircu- 

21 


864 


THE  SPECIAL  SENSES. 


c 
c 

E 

h 

In 

M 
I 


lar  canals  is  suspended  free  in  the  perilymph  and  receives 
the  sounds  through  the  medium  of  that  fluid,  while  on  the 
other  hand  the  lamina  spiralis  upon  which  the  cochlear 
nerve  is  expanded  is  continuous  with  the  solid  walls  of  the 
cochlea  from  which  it  receives  impressions  directly.  The 
function  of  the  rods  of  Corti  is  probably  to  receive  impres- 
sions of  various  notes  and  tones,  and  communicate  them  to 
the  brain  through  the  filaments  with  which  the  rods  are 
connected.  The  intensity  of  a  sound  is  due  to  the  length  of 
the  vibrations,  the  'pitch  to  the  number  in  a  second,  and  the 
quality  to  the  number  of  secondary  notes.  The  power  of 
determining  the  direction  and  distance  of  sounds  is  ac- 
quired by  experience. 

Any  irritation  or  excitement  of  the  auditory  nerve,  as 
congestion,  cerebral  disease,  etc.,  may  give  rise  to  ringing 
or  buzzing  sounds  in  the  ears.  These  are  called  subjective 
sounds,  because  they  are  produced  by  internal  causes. 

The  sense  of  hearing  varies  much  in  different  individuals, 
and  in  the  same  individual  at  different  times ;  some  will 
discern  the  most  delicate  sounds  without  the  least  difficulty, 
whilst  others  are  wholly  incapable  of  receiving  similar  im- 
pressions. Hearing  may  be  impaired  by  a  preternaturally 
dry  state  of  the  membrana  tympani,  or  the  partial  closure 
of  the  external  meatus  by  collections  of  wax,  particles  of 
dust,  etc.  In  some  of  the  lower  animals,  the  sense  of  hear- 
ing is  very  acute. 

SENSE   OF    TASTE. 

The  principal  organs  of  the  sense  of  taste,  are  the  tongue 
and  fauces.  The  conditions  necessary  are  the  presence  of 
special  nerves  to  convey  the  impressions  received,  and  the 
excitation  of  these  nerves  by  sapid  matters  in  a  state  of 
solution.  The  nerves  are  the  lingual  branch  of  the  fifth,  and 
the  glosso-pharyngeal  (p.  333).  The  tongue  is  a  muscular 
organ,  covered  with  mucous  membrane  andpresentsnuraerous 
papillae.  These  have  been  already  described  (p.  107).  The 
muscles  are  divided  into  intrinsic,  or  those  that  form  the 


receives 
e  on  the 

cochlear 
Us  of  the 
;ly.  The 
e  impres- 
}  them  to 

rods  are 
length  of 
,  and  the 
power  of 
Is    is  ac- 

oerve,  as 
)  ringing 
ruhjective 
5es. 

ividuals, 
Dine  will 
lifficulty, 
Qilar  ira- 
laturally 
1  closure 
:'ticles  of 
of  hear- 


e  tongue 
isence  of 
and  the 
state  of 
ifth,  and 
nuscular 
uraerous 
7).  The 
orm  the 


SENSE  OF  TASTE. 


365 


greater  part  of  the  substance  of  the  tongue,  as  the  lingual es  -^ 
and  extrinsic  or  those  which  attach  it  to  surrounding  parts, 
as  the  hyo-glossus,  genio-hyoglossus,  stylo-glossus,  etc. 
The  epitiieliura  of  the  tongue  is  of  the  squamous  variety. 

Fig.  120. 


The  tongue  with  its  papilla;  and  nerves.  1,  Hypogii)ssal  nerve.  2,  Lingual  branch  of 
the  trifacial.  3,  Lingual  branch  of  the  glosso-pharyngeal  nerve.  4,  Chorda  tynipani.  «, 
Sub-maxillary  ganglion.  11,  Anastomoses  of  the  lingual  with  the  hyi)oglossal  uerve.  12, 
Facial  nerve.'  13  Mucous  membrane  detached  and  thrown  upwards  ;  thi  circumvallate 
papilla)  aie  seen  behind.    (Hirschfeld.) 

and  covers  every  part  of  the  surface,  but  is  thinner  in  some 
parts  than  others,  as  on  the  fungiform  papillre.  Peculiar 
structures,knowii  as  taste  huds  or  taste  goblets,ha.ve  been  dis- 
covered in  the  circumvallate  papillje  and  on  the  posterior 
surface  of  the  epiglottis.  They  are  oval  in  shape,and  con- 
sist of  narrow  fnsif orm  gustatory  cells  surrounded  by  a  layer 
of  broader  fusiform  or  encasing  cells  (Fig.  121).  A  depress- 
ion exists  in  the  epithelium  over  the  goblet,  and  the  gusta- 
tory cells  present  hair  like  processes  which  resemble  cilia. 
These  bodies  are  found  side  by  side  in  considerable  nura- 
bers,and  are  believed  to  be  gustatory  in  function,  but  as  yet 
no  nerves  have  been  traced  into  them. 

The  fauces,  uvula,  tonsils,  and  upper  part  of  the  pharynx, 
all  of  which   are   supplied  with   branches   of  the  glosso- 


366 


THE  SPECIAL  SENSES. 


\ 


t 


v.. 


pliaryngeal  nervc,are  endowed  with  the  sense  of  taste.  In 
most  persons  the  sense  of  taste  is  most  acute  in  the  tip  and 
edges  of  the  tongue;  while  in  the  middle  of  the  dorsum  it  is 
feeble. 

The  tongue  also  possesses  an  accurate  sense  of  touch,  and 
Fig.  121.  is  capable  of  receiving  im- 

pressions of  heat  or  cold, 
pain,  mechanical  pressure, 
and  the  form  of  surfaces.  Its 
common  sensibility  may  be 
impaired  or  lo-^t,  and  the 
sense  of  taste  still  continue. 
The  nerve  fibres  for  these 
two  sensations,  although 
found  in  the  same  papilla3, 
distinct,  just  as  the 
nerves  and  the 
nerves  of  common  sensation  in  the  nose  are  dis- 
tinct. The  senses  of  smell  and  taste  are  closely 
associated,  for  if  the  former  be  impaired  or  lost  as  in  disease, 
the  latter  is  rendered  less  acute.  Taste  appears  to  be 
governed  to  some  extent  by  the  same  principles  as  that  of 
sight ;  viz.  that  those  tastes  which  are  opposite  or  comple- 
mentary, render  each  other  more  distinct,  as  sweet  and  bitter 
acid  and  alkaline,  etc.  The  sense  of  taste  is  very  delicate 
though  not  to  be  compared  with  the  sense  of  smell.  It 
may  be  rendered  less  distinct  in  regard  to  any  substance  by 
constant  contact  with  it,  in  the  same  way  as  the  eye  becomes 
fatigued  with  the  constant  perception  of  a  single  color 
Subjective  sensations  of  taste  frequently  occur  in  diseased 
conditions  of  the  nerves  of  taste,  or  their  associate  nerves. 


Taste  goblet;  a,  depression  in  the  epitlioliuiu   ai'C 
over  the  goblet ;  b,  nuclei  of  encasini!;  cells;      . 
c,  two  nuclei  of  the  gustatorj'  cells.  oliactory 


SENSE  OF  TOUCH. 

The  sense  of  touch  has  a  wider  range  than  the  other 
senses,  and  varies  greatly  in  the  different  parts  of  the  body. 
It  is  greatest  at  the  extremities  of  the  fingers,  lips  and 


SENSE  OF  TOUCH. 


367 


taste.  In 
le  tip  and 
rsum  it  is 

ouch,  and 

iviug  im- 

or    cold, 

pressure, 

rfaces.  Its 

yi^  may  be 

and    tlie 

continue. 

for   these 

although 

e  papillae, 

as     the 

and    the 

are     dis- 

closely 

in  disease, 

irs   to  be 

as  that  of 

comple- 

and  bitter 

i  delicate 

3mell.     It 

stance  by 

e  becomes 

gle   color 

L  diseased 

nerves. 


the  other 

the  body. 

lips  and 


tongue,  and  least  in  the  integument  of  the  trunk,  arms  and 
thighs  (p.  124).     There  are  no  special  nerves  of  the  sense  of 
touch ;  they  are  simply  the  nerves   of  common  sensation 
supplied  to  all  parts  of  the  body,  and  hence  it  is  that  all 
parts  are  endowed  with  this  sense.     Touch  is  simply  an  ex- 
altation of  common  sensation.     Some  are  of  the  opinion, 
that  common  sensation  and  tactile  sensation  are  communi- 
cated to  the   sensorium  through   different  sets  of  nerves. 
Those  parts  of  the  body  in  which  the  sense  of  touch  is  most 
acute  are  abundantly  provided  with  papilUe,  which  increase 
the  extent  of  surface  for  nerve  distribution.     These  papilUe 
vary  in  size  from  t'io  to  ^i^  of  an  inch  (.25  to  .1  mm).     The 
nerves  distributed  to  them  are  destitute  of  the  white  sub- 
stance of  Schwann,  and  ap-  fi?.  122. 
pear  to  terminate  in  oval- 
shaped  bodies,   formed    of 
connective    tissue     named 
tactile  corpuscles  (Fig.  122, 
a).      In   some  of  the   pa- 
pillae, as  those  of  the  lips, 
tongue,  palate  and  integu- 
ment of  the  glans  penis,  the 
nerves  terminate  in  small 
round    bodies,    ttJo    of  an 
inch  (42   mmm,)  in  diam- 
eter,    the    end     bulbs    of      ^   ^^^^,.^^  cor,.u.sdo ; 

KraUSe(Fig.   122,B).    In   the      Kra«se  (see  pa^jo  2sT). 

palms  of  the  hands,  points  of  the  fingers  and  soles  of  the 
feet,  the  papillae  are  arranged  in  rows,  and  form  ridges  and 
furrows  which  may  be  seen  with  the  naked  eye  (p.  116). 
The  sense  of  touch  is  peculiar  from  being  widely  distributed; 
even  the  eyelashes,  hair  (near  the  root),  nails  and  teeth  ex- 
hibit this  sense  in  a  manner  peculiar  to  themselves.  The 
integument  is  endowed  not  only  with  the  sense  of  touch,  per 
se,but  also  with  the  ^Qn^Qoipressvire^temperatiive  audpam  ; 
the  latter  being  a  highly  exalted  sensation  of  the  three  former. 


368 


THE  SPECIAL  SENSES. 


c 


I 


I 

Hi 


Hi 


Some  parts  of  the  body  are  sensitive  to  tickling  as  the  axilla) 
a,nd  soles  of  the  feet,  but  are  comparatively  blunt  in  regard 
to  the  special  sense  of  touch. 

The  sense  of  touch  enables  the  mind  to  become  acquainted 
with  the  condition  of  bodies,  whether  hot  or  cold,  rough  or 
smooth,  hard  or  soft,  wet  or  dry,  and  their  size,  form,  etc. 
The  organs  by  which  touch  is  chiefly  exercised,  are  the 
hands,  and  especially  the  points  of  the  fingers,  which  are 
abundantly  provided  with  papillae  for  that  purpose.  The 
variation  in  sensibility  in  different  parts  may  be  determined 
by  the  aid  of  a  pair  oi'  compasses.  Thus  the  two  ]:)oints  of 
a  pair  of  compasses  may  be  separately  distinguished  by  the 
point  of  the  finger  when  only  about  one-third  to  one-half  a 
line  apart,  while  they  require  to  be  twenty  to  thirty  lines 
apart,  to  be  separately  felt  on  the  integument  of  the  spine, 
arm,  thigh,  sacral  or  gluteal  region.  The  two  points  are  f  ^It 
separately  on  the  tip  of  the  tongue  when  i^  of  an  inch 
apart,  on  the  middle  of  the  dorsum  of  the  tongue,  \  of  an 
inch,  on  the  lip  \  of  an  inch,  and  on  the  tip  of  the  nose, 
when  \  of  an  inch  apart.  The  CBsthesio7nete7%  an  instrument 
for  determining  the  relative  sensibility  of  the  arms  or  legs 
in  paralysis,  is  constructed  on  this  principle.  The  sense  of 
touch  may  he  very  much  increased  by  constant  practice,  as 
is  seen  in  the  case  of  the  blind,  who  acquire  a  remarkable 
facility  for  reading  raised  letters,  by  the  aid  of  the  fingers. 

The  sense  of  pressure  is  produced  by  weight  or  tension, 
and  is  intensified  according  to  the  increase  of  the  weight 
or  tension.  In  lifting  a  body  we  judge  of  its  weight  partly 
by  the  pressure  on  the  hands,  and  partly  by  the  amount  of 
muscular  force  used  in  raising  it.  The  latter  is  called  the 
Tnuscular  sense  (p.  309).  These  two  faculties  give  us  the 
power  of  discerning  the  relative  weight  of  bodies.  We 
have  also  the  power  of  estimating  beforehand, and  regulating 
the  amount  of  muscular  force  required  in  lifting  heavy 
bodies.  If  we  attempt  to  lift  an  object  which  we  have 
conceived  to  be  heavier  than  it  really  is,  we  are  liable  to  be 


SENSE  OF  TEMPERATURE. 


369 


the  axillae 
in  regard 

cquainted    . 
,  rough  or 
form,  etc. 
I,  are  the 
which  are 
ose.     The 
etermined 
)  points  of 
led  by  the 
one-half  a 
lirty  lines 
the  spine, 
ats  are  f  3lt 
f  an   inch 
ue,  \  of  an 
f  the  nose, 
nstrument 
ms  or  legs 
16  sense  of 
practice,  as 
-emarkable 
le  fingers, 
or  tension, 
the  weight 
ight  partly 
amount  of 
5  called  the 
jive  us  the 
odies.     We 
I  regulating 
'ting  heavy 
h  we  have 
liable  to  be 


overturned  by  the  muscular  effort  unnecessarily  put  forth 
to  overcome  the  supposed  resistance. 

The  sense  of  temperature  is  distinct  from  that  of  touchy 
and  may  remain  unimpaired  when  the  latter  is  for  the  time 
in  abeyance,  as  when  a  nerve  is  pressed  upon  or  partly  in- 
jured. The  sensations  of  temperature,  however,  are  very 
deceptive,  and  cannot  be  relied  upon;  as  e.g.  in  the  cold  stage  of 
disease,  the  patient  feels  excessively  cold,  while  the  ther- 
mometer shows  that  the  temperature  is  over  100"F.  Again, 
if  one  hand  be  put  in  cold  water,  and  the  other  in  water  at 
a  temperature  of  110°F.,  and  both  are  then  immersed  in 
water  at  80°F.,  it  will  feel  warm  to  the  hand  previously  in 
the  cold  water,  and  cold*  to  the  other.  In  examining 
patients  in  cases  of  fever  or  inflammation,  in  regard  to  the 
heat  of  the  skin,  no  reliance  can  be  placed  on  the  sensation 
of  heat  communicated  to  the  hand,  and  therefore  the  ther- 
mometer should  always  be  used.  Some  parts  of  the  body 
will  bear  a  higher  degree  of  temperature  than  others,  e.g., 
the  hand  will  resist  a  temperature  which  would  be  intoler- 
able to  the  body.  Only  ordinary  temperatures  can  be  dis- 
criminated, viz.,  from  50°  to  120°F. ;  very  high  or  very  low 
temperatures  produce  a  burning  sensation.  Subjective  sen- 
sations of  touch,  arising  from  some  internal  causes,  are  of 
frequent  occurrence,  as  heat,  cold,  rigor,  neuralgic  pains, 
itching,  formication,  etc. 


370 


THE  VOICE. 


CHAPTER    XV. 


VOICE. 


\ 


C 

t 

^ 


Hi 

if 


The  Larynx  is  the  organ  of  voice,  and  is  situated  at  the 
upper  part  of  the  air  passage,  between  the  trachea  and 
base  of  the  tongue,  at  the  upper  and  anterior  part  of  the 
neck.  It  is  narrow  and  cylindrical  below,  but  is  wide  and 
triangular  at  the  upper  part.  It  is  composed  of  cartilages, 
which  are  held  together  by  ligaments,  and  acted  upon  by 
numerous  muscles.  It  is  lined  by  mucous  membrane, 
covered  with  columnar  ciliated  epithelium  below  the  super- 
ior vocal  cords  and  the  upper  part  in  front;  the  rest  of  its 
extent  is  covered  with  squamous  epithelium.  The  upper  part 
of  the  larynx  presents  a  triangular-shaped  orifice,  wider  in 
front  than  behind — the  glottis.  This  opening  is  guarded  by 
the  epiglottis,  which  is  situated  in  front,  between  the  open- 
ing and  the  root  of  the  tongue.  The  epiglottis  closes  the 
orifice  during  the  passage  of  food  or  fluids,  and  prevents 
their  passage  into  the  larynx.  Within  the  cavity  of  the 
larynx,  on  each  lateral  wall,  may  be  seen  two  elevated 
bands,  the  superior  and  inferior  vocal  cords,  separated  by 
an  elliptical  depression — the  ventricle  of  the  larynx  (Fig. 
Ill  /,)  p.  341.  Of  the  two  vocal  cords,  the  inferior  consists 
of  a  band  of  yellow  elastic  tissue,  covered  by  mucous  mem- 
brane, and  is  called  the  true  vocal  cord;  while  the  superior, 
which  is  formed  entirely  by  a  folding  of  the  mucous  mem- 
brane, is  called  the  false  vocal  cord,  because  it  is  not  con- 
cerned in  the  production  of  the  voice.  It  is  in  the  larynx  that 
the  sounds  are  originally  produced;  but  they  may  be  modified 
during  and  after  their  production  by  the  tongue,  palate, 


^ 


GLOTTIS  AND  VOCAL  CORDS. 


371 


Fig.  123. 


teeth,  lips,  etc.,  constituting,  in  man,  the  faculty  of  speech. 
The  interval  between  the  true  vocal  cords  in  the  median 
line  is  called  the  rvnxa  glottidis,  or 
chink  of  the  glottis,  the  narrow- 
ing or  widening  of  which,  and 
the  tension  or  laxity  of  the  cords, 
produce  those  variations  of  sound 
which  are  characteristic  of  the 
human  voice.  The  narrower  the 
opening  and  the  tenser  the  cords, 
cceteris  paribus,  the  higher  the 
pitch  of  the  note.    The  tension  of     „, 

1     1         •  PI  Olottm  seen  ivith   the  lar>in(/nncope 

the  vocal  cords  and  the  size  of  the    dnnwj  the  emix«i„n  o/  hiijh-pUched 

sounds.— I,  2,  base  of  the  toll^me ;  3, 

aperture,  are  regulated  by  mus-  *.  epi^'iottis ;  .5, «,  pharynx ;  7,  ary- 

^  o  ^  teiioiU  cartilages ;  8,  o))eniii>f  between 

CleS    which    are    situated    in    the    t"?**^ ^tt-^e  vocal  conls ;  O,  aryteno-epl- 

(f lottidean  folds ;  10,  cartilage  of  Siin- 

larvnX.         It     has      been      IJrOVed    ^o""'.;    ^l-   cnnelfonn  cartilage;    12, 

•'  A  superior    vocal    cords;    13,    inferior 

by  observation  on  the  living  vocai cord8.-{Le  Bon.) 
subject,  as  well  as  by  experiments  on  the  larynx  of  the  dead 
body,  that  the  sound  of  the  voice  is  caused  by  the  vibration 
produced  by  the  currents  of  expired  air  passing  over  the 
margins  of  the  true  vocal  cords.  For  example,  if  a  free 
opening  be  made  in  the  trachea,  the  sound  of  the  voice 
eeafes,  but  returns  as  soon  as  the  opening  is  closed.  Again, 
distinct  vocal  sounds  may  be  produced  in  the  dead  subject 
by  forcing  a  current  of  air  through  the  larynx,  and  this  will 
occur  even  when  all  the  structures  above  the  vocal  cords 
are  removed. 

The  essential  parts  of  the  larynx  are  the  thyroid  carti- 
lage, the  cricoid  cartilage,  the  two  arytenoid  cartilages  and 
the  true  vocal  chords.  The  latter  are  attached  behind  to  the 
front  portion  of  the  base  of  the  arytenoid  cartilages,  and  in 
front  to  the  depression  between  the  two  alse  of  the  thyroid 
cartilage,  so  that  all  movements  of  the  arytenoid  cartilages 
produce  an  effect  on  the  vocal  cords.  Movements  of  the 
cricoid  cartilage  also  produce  an  effect  on  the  vocal  cords 
indirectly,  since  the  arytenoid  cartilages  rest  upon  its  poste- 


372 


THE  VOICE. 


an 


til 


rior  part.  Those  muscles  which  act  upon  the  arytenoid  car- 
tilages either  directly  or  indirectly,  nine  in  number,  are 
calle'l  the  intrinsic  muscles  of  the  larynx,  viz. :  two  crico- 
thyroid muscles,  two  thyro-arytenoid,  two  posterior  crico- 
arytenoid, two  lateral  crico-arytenoid,  and  one  arytenoid 
muscle.  The  crico-thyroid,  produce  tension  and  elongation 
of  the  vocal  cords  by  drawing  downwards  and  forwards  the 
thyroid  cartilage  over  the  cricoid.  The  thyro-arytenoid 
draw  the  arytenoid  cartilages  forwards  towards  the  thyroid 
and  relax  the  vocal  cords.  The  posterior  crico-arytenoid 
rotate  the  base  of  the  arytenoid  cartilages  outwards 
and  backwards,  separate  the  vocal  cords  and  open  the 
glottis.  The  lateral  crico-arytenoid  rotate  the  arytenoid 
cartilages  inwards  and  close  the  glottis.  The  arytenoid  mus- 
cle approximates  the  arytenoid  cartilages  and  closes  the 
glottis,  especially  at  its  postei'ior  pjst.  The  nerves  which 
govern  these  actions  are  the  branches  of  the  pneumogastric 
and  spinal  accessory  (p.  333). 

The  combined  action  of  the  muscles  places  the  vocal 
cords  in  the  various  positions  necessary  for  breathing  and 
the  production  of  sounds,  as  in  singing,  speaking,  etc.  In 
ordinary  tranquil  breathing  the  opening  of  the  glottis  is 
wide  and  triangular,  and  becomes  a  little  narrower  at  each 
expiration.  In  the  production  of  sound  it  is  narrowed,and 
the  tension  of  the  vocal  cords  increased.  In  the  production 
of  higher  notes  the  vocal  cords  are  more  closely  approxi- 
mated and  rendered  more  tense  (Fig.  123).  In  the  space 
between  the  arytenoid  cartilages  at  the  posterior  part  of  the 
glottis,  no  regular  vocal  sound  is  produced,  nothing  more 
than  a  mere  rustling  or  gurgling  sound.  The  tone  of  the 
voice  is  somewhat  lowered  by  the  action  of  the  epiglottis 
when  it  partially  covers  the  cavity  of  the  larj'^ux.  The  ven- 
tricles of  the  larynx  are  for  the  purpose  of  affording  free 
space  for  the  vibrations  of  the  vocal  cords. 

The  modes  of  sequence  of  the  notes  of  the  voice  are  three 
in  number ;  1st.  The  monotonous,  as  in  ordinary  speaking, 


I 


COMPASS  OF  THE  VOICE. 


373 


vocal 


with  occasional  intonation  for  the  sake  of  accent  ;  2nd,  the 
transitional,  from  high  to  low  notes  and  vice  versa  with- 
out intervals ;  such  as  in  crying  in  man,  and  the  howling 
of  animals,  and  3rd,  the  musical,  in  which  each  note  has  a 
determinate  number  of  vibrations. 

The  compass  of  the  voice  varies  in  different  individuals 
from  one  to  three  octaves,  and  some  singers  may  even  ex- 
ceed three  octaves.  Before  pubert}',  the  pitch  of  the  male 
and  female  voice  is  nearly  the  same,  the  male  voice  being  a 
little  louder ;  but  at  this  period  the  larynx  of  the  male 
undergoes  certain  changes,  during  which  the  voice  is  said 
to  "  crack,"  and  the  pitch  falls  about  one  octave.  This 
change  does  not  take  place  in  eunuchs,  and  they  retain  the 
puerile  character  of  the  voice.  The  different  pitch  of  the 
male  and  female  voice  depends  on  the  different  length  of 
the  vocal  cords  in  the  two  sexes,  viz.  :  as  three  to  two 
respectively^  The  lowest  note  of  the  female  voice  is  an 
octave  higher  than  the  lowest  note  of  the  male  voice,  and 
the  compass  of  the  two  is  about  four  octaves.  There  arc  two 
kinds  of  male  voice,  the  bass  and  tenor,  and  also  two  kinds 
of  female  voice,  the  contralto  and  soprano,  all  differing  from 
each  other  in  tone.  The  bass  voice  reaches  lower  than  the 
tenor,  and  its  strength  lies  in  the  low  notes;  while  the 
soprano  reaches  the  highest  in  the  scale.  The  essential  dis- 
tinction between  the  different  voices,  however,  consists  in 
the  tone  which  distinguishes  them  when  they  are  singing 
the  same  note.  Most  persons  have  the  power  of  modulating 
their  voices  through  a  double  series  of  notes  of  different 
characters,  viz. ;  the  chest  notes  or  the  notes  of  the  natural 
voice,  and  the  falsetto  notes.  The  former  are  produced  by 
the  ordinary  vibrations  of  the  vocal  cords  and  are  much 
stronger  ;  the  latter,  in  all  probability,  by  the  vibration  of 
only  the  inner  border  of  the  vocal  cords,  and  are  of  a  fiute- 
like  cha^'acter. 

The  voice  is  principally  used  in  man  in  the  formation  of 
speech.     The  tone  of  the  speech  depends  much  upon  the 


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THE  VOICE. 


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state  of  the  chordse  vocales,  and  the  development  of  the 
larynx  ;  but  articulation,  or  modification  of  the  sounds,  is 
effected  by  the  lips,  teeth,  mouth,  tongue,  fauces  and  nose. 
Articulate  sounds,  or  the  sounds  produced  in  speech,  are  com- 
monly divided  into  vowels  and  consonants  ;  the  former  are 
sounded  by  the  larynx,  while  the  latter  are  produced  by  the 
interruption  of  the  current  of  air  above  the  larynx.  All 
vowel  sounds  can  be  expressed  in  a  whisper,  without  vocal 
tone — -mutely.  During  the  production  of  the  vowel  sounds 
the  posterior  nares  are  closed,  and  no  air  issues  through  the 
nose.  The  consonants  cannot  be  sounded  except  conso- 
nantly with  a  vowel,  hence  the  name.  They  are  divided  into 
labial,  dental  or  guttural,  according  to  the  interi-uption  to 
the  current  of  air  required  in  their  formation,  as  by  the  lips, 
teeth,  palate  or  pharynx.  They  may  also  be  classified  ac- 
cording to  the  character  of  the  movements  which  give  rise 
to  them,  as  explosives,  as  p,  b,  t,  d,  etc.,  aspirates,  as/",  v,  s, 
I.  z,  etc.,  resonants,  as  m,  n,  ng,  etc.,  and  vibratory  as  r. 

Ventriloquism  appears  to  consist  in  the  varied  modifica- 
tion of  the  sounds  produced  in  the  larynx,  so  as  to  imitate 
the  voice  as  heard  from  a  distance.  It  is  accomplished  by 
taking  a  full  inspiration,  then  keeping  the  muscles  of  the 
neck  and  chest  fixed,  and  speaking  with  the  mouth  almost 
closed  and  the  lips  motionless,  while  air  is  slowly  expired 
through  a  narrow  glottis,  care  being  taken  that  none  of  the 
expired  air  passes  through  the  nose  The  attention  of  the 
audience  is  at  the  same  time  generally  directed  to  that  part 
of  the  room  from  which  the  sound  is  expected,  a  circum- 
stance which  adds  materially  to  the  success  of  the  perform- 
ance. 

Stammering,  in  most  instances,  is  an  affection  of  the 
nervous  system,  and  aot  of  the  articulating  organs.  It  con- 
sists in  an  imperfect  power  of  co-ordinating  the  muscles  of 
speech,  associated  with  a  spasmodic  action  of  certain  mus- 
cles concerned  in  the  formation  of  the  '"oice.  Some  stam- 
mer only  on  attempting  to  articulate  certain  letters  ;  others 


REPRODUCTION. 


375 


at  of  the 
;ounds,  is 
and  nose. 
,  are  com- 
ormer  are 
ed  by  the 
>^nx.     All 
out  vocal 
el  sounds 
rough  the 
pt  conso- 
/ided  into 
•uption  to 
Y  the  lips, 
isified  ac- 
tive rise 
as  J,  V,  s, 
y  as  r. 
modifica- 
o  imitate 
ished  by 
es  of  the 
1  almost 
expired 
ne  of  the 
•u  of  the 
bhat  part 
cireum- 
Derforra- 

n  of  the 
It  con- 
uscles  of 
ain  raus- 
ne  stam- 
ofchers 


do  so  at  every  attempt  to  speak.  It  is  much  increased  by 
any  mental  excitement,  surprise,  etc.  Females  seldom  stam- 
mer, although  more  subject  to  nervous  disorders  generally 
than  males.  The  cure  of  stammering  is  best  effected  by 
training  the  muscles  in  the  production  of  the  sounds  most 
easily  formed,  and  thence  proceeding  to  the  most  difficult  ; 
to  avoid  all  causes  of  excitement  to  the  patient,  and  prevent 
him  from  thinking  about  his  condition  as  much  as  possible 
Some  have  recommended  the  use  of  pebbles  in  the  mouth, 
or  small  pieces  of  ivory  ;  but  it  is  very  doubtful  whether  or 
not  these  can  be  of  any  great  service. 


CHAPTER  XVI. 


REPRODUCTION. 

The  process  of  reproduction  comprises  the  several  provi- 
sions made  for  the  multiplication  o-  individuals  and  the 
propagation  of  the  species.  There  are  three  modes  by  which 
the  multiplication  of  individuals  takes  place  in  the  lower 
orders  of  organized  beings,  while  in  the  higher  forms  it  is 
restricted  to  one  of  these  types. 

The  first  and  simplest  mode  consists  in  the  division  of 
the  being  into  two,  each  of  these  again  subdividing  into  two 
others/and  so  on.  This  is  multiplication  by  subdivision ;  or 
fissiparous  multiplication  (Fig.  124).  It  is  seen  in  the  lowest 
plants,  as  in  the  cells  of  fungi  and  lichens,  and  also  in  carti- 
ageand  other  cells  of  the  human  body.  The  amoeba  also 
furnishes  a  good  example  of  this  mode  of  reproduction.  It 
throws  out  a  large  process  in  a  certain  direction,  becomes 
contracted  at  or  near  the  middle,  and  divides  into  two  or 
more  parts,  each  containing  a  portion  of  the  original  nucleus. 
Some  organizations,  as  the  polyp,  when  divided  artificially 


1 


mm 


376 


REPRODUCTION. 


c 

\ 

•n 

In 


into  segments,  have  the  power  of  developing  into  a  perfect 
form  from  each  segment. 

The  second  mode  takes  place  by  a  process  of  gemmation, 
or  budding  from  the  parent  stalk.  These  buds,  which  con- 
sist of  a  mass  of  cells,  are  at  first  entirely  nourished  by  the 
parent  stalk,  but  gradually  become  less  dependent,  and  at 


Fipr.  124. 


Fife'.  125. 


A  coll  uiiilergoing  the  process  of  inultiiilica- 
tioii  by  sulHlivisioii  ;  a,  original  cell ;  b,  coll  be- 
coming oval ;  c,  undergoing  hour-glass  ^lontrac- 
tion  ;  d,  division  of  the  cell  into  two. 


Amoeba  ;  in  the  centre 
is  seen  the  nui  'ens  and 
surrounding  it  a  number 
of  vacuoles  and  granules 


last  detach  themselves  and  maintain  a  separate  existence. 
This  is  termed  multiplication  by  gemmation  or  geTumipar- 
ous  multiplication.  The  hydra  affords  a  good  example  of  this 
variety.  The  first  change  which  is  observed  is  a  slight  ele- 
vation on  the  surface,  which  assumes  a  globular  form ;  a 
cavity  is  then  formed  in  the  interior,  which  communicates 
with  the  parent.  After  a  time  this  channel  of  commnnica- 
tion  closes,  ^the  newly-formed  polyp  drops  off,  and  a  new 
creature  is  formed.  The  joints  of  the  common  tape-worm 
multiply  in  this  manner.  This  process  is  also  common 
among  the  Bryozoj,,  and  leads  to  the  formation  of  colonies. 

The  third  Tnode  is  called  true  generation,  and  consists  in 
the  union  of  the  contents  of  two  different  cells,  the  sperm 
cell  and  the  germ  cell,  from  which  is  produced  a  new  being 
differing  from  both.  The  simplest  form  of  this  process  is 
seen  in  the  Algae  in  conjugation.  At  first  the  opposite  cells 
of  two  filaments  form  a  process  on  the  sides  next  each  other ; 
these  at  length  meet  and  fuse,  and  the  contents  of  the  two 
cells  become  mixed  and  form  a  new  body  termed  a  spore 
or  sporangium,  from  which  the  new  plant  is  formed. 


>  a  perfect 

imviation, 
s^hich  con- 
ed by  the 
it,  and  at 

ST.  125. 


in  the  centre 
mil  'eiia  and 
;  it  a  number 
md  granules 

existence. 
emmipar- 
spleof  this 
slight  ele- 
form  ;  a 
municates 
mmnnica- 
nd  a  new 
ape-worm 
common 
colonies, 
onsists  in 
he  sperm 
lew  being 
process  is 
osite  cells 
ch  other ; 
■  the  two 
d  a  spore 
id. 


ACTION  OF  THE  MALE. 


377 


In  the  higher  plants  and  animals  distinct  organs  are  set 
apart  for  the  formation  of  the  sperm  cells  and  germ  cells  ; 
the  former  are  produced  by  the  male  organs  of  generation, 
the  latter  by  the  female.  Through  the  action  of  the  con- 
tents of  the  sperm  cell  the  ovum  becomes  impregnated,  and 
an  embryo  is  formed  from  which  the  adult  animal  is  gradu- 
ally developed.  In  some  instances,  however,  as  in  the  class 
of  insects,  several  distinct  changes  or  metamorphoaes  are 
passed  through  before  the  animal  is  fully  developed,  as  the 
larva,  chrysalis,  and  perfect  animal.  In  other  instances  the 
embryo,  instead  of  being  developed  into  the  perfect  animal, 
only  attains  a  sort  of  larval  condition,  and  there  may  be 
several  series  of  these  imperfect  or  larval  forms,  each  larva 
producing  other  larvse,  until  at  last  they  give  rise  to  perfect 
forms,  which  propagate  only  by  the  production  of  ova.  This 
is  called  by  Prof  Owen  "r.ietageaens. 

Action  of  the  Male. — The  male  furnishes  the  sperma- 
tic fluid  or  sperm,  which  is  secreted  by  the  testes.  This 
fluid   contains   the   sperm    cells    in  Fi^'.  126. 

which  are  developed  the  sperma- 
tozoa; also  an  albuminous  substance^ 
various  salts  and  an  animal  substance 
resembling  fibrin  termed  sperma- 
tine.  The  sperm  cells  are  large 
spherical  vesicles,  in  which  are  con- 
tained from  two  to  nine  smaller  cells 
or  nuclei,  in  each  of  which  is  found 

,  rT\^  L  ii.  Human  spermatozoa  magnified 

a     spermatozoon,        ihe     spermatozoa  .V)0  diameters ;  b,  sperm  cell  con- 

, ,  I'll  1        /» ii  taining  the  spermatozoon  coiled 

are  the    isential  elements  01  the  spe"-  up  within  it ;  c,  ceii  elongated  by 

,.      n     '  1  1  If  1  ,1       tn^  partial  uncoiling  of  the  sper- 

matic fluid,  and  are  set  tree  by   the  matozoon. 

breaking  down  of  the  sperm  cells  (Fig,  126  ,a).  They  are 
transparent  filamentous  bodies,  about  *"®  of  an  inch  (42 
mmm.)  in  length,  and  from  s-^s  to  Tir^Tny  of  an  inch  (5  to 
25  mmm.)  in  thickness,  being  thicker  at  the  anterior  ex- 
tremity or  head  than  the  posterior  or  tail.  Their  move- 
ment is  accomplished  by  the  constant  vibration  of  the  tail ; 


378 


REPRODUCTION. 


\ 
ft, 

k 


they  are  said  to  move  at  the  rate  of  one  inch  in  seven 
and  one-half  minutes.  Their  movem'^nts  may  be  sus- 
pended, and  their  power  of  impregnation  destroyed  by 
profuse  leucorrhceal  discharges  or  acrid  secretions  of  the 
vagina,  and  by  the  action  of  solutions  which  act  chemically 
upon  them,  as  solution  of  silver  nitrate,  zinc  sulphate,  zinc 
chloride,  etc.  In  the  female  organs  of  generation  the  move- 
ments continue  longer  than  in  any  other  situation. 

In  the  act  of  coition  the  seminal  fluid  is  deposited  in  the 
vagina,  and  the  spermatozoa  make  their  way  into  the  uierus 
and  meet  the  ovum  at  or  soon  after  its  discharge  from  the 
ovary.  One  or  more  are  supposed  to  pierce  the  vitelline 
membrane  and  pass  into  the  interior  of  the  ovum  or  germ 
cell,  and  unite  with  it,  after  which  they  disappear.  It  is  also 
supposed  by  some  that  they  enter  through  a  small 
opening  or  micrapyle,  and  by  others  that  they  perforate 
the  vitelline  membrane.  The  fecundation  of  the  egg  may 
take  place  eititer  in  the  uterus,  Fallopian  tube,  or  ovary,  in 
each  of  which  situations  spermatozoa  have  been  found  after 
coition.  The  high  degree  of  nervous  excitement  which 
att  3nds  the  act  of  coition,  is  followed  by  a  corresponding 
amount  of  depression,  and  the  too  frequent  repetition  of  it 
is  very  injurious  to  the  general  health.  This  is  still  more 
the  case  with  that  solitary  vice,  which  it  is  to  be  feared  is 
practised  by  too  many  youths.  Nothing  is  more  certain  to 
reduce  the  powers  both  of  body  and  mind,  than  excesses  iu 
this  respect. 

Action  of  the  Fjiimale. — The  essential  parts  of  the 
female  organs  of  generation,  and  counterpart  of  the  testes, 
are  the  ovaries,  in  which  the  ova  are  developed.  Each 
ovary  is  about  an  inch  and  a  half  long,  three-fourths  of  an 
inch  wide,  and  half  an  inch  in  thickness,  and  is  attached  to 
the  uterus  by  the  ligament  of  the  ovary,  and  to  the  Fallo- 
pian tube  by  one  of  the  fimbriae,  the  rest  of  the  surface  being 
covered  with  columnar  epithelium,  beneath  which  is  the 
proper    covering  of  the  organ — the    tunica    albuginea — 


ACTION  OB   THE  FEMALE. 


379 


in  seven 
'  be  sus- 
royed  by 
»ns  of  the 
hemically 
hate,  zinc 
the  move- 
n. 

ed  in  the 
the  uierus 
I  from  the 
?  viteUine 
m  or  germ 
,   It  is  also 
L   a    small 
■  perforate 
;  egg  may 
r  ovary,  in 
bund  after 
snt    which 

esponding 
ition  of  it 

still  more 
feared  is 

certain  to 

xcesses  in 

'ts  of  the 
Ithe  testes, 
ed.  Each 
rths  of  an 
Ittached  to 
Ithe  Fallo- 
rface  being 
|ich  is  the 
mginea — 


which  is  a  dense,  firm  membrane,  enclosing  the  parenchyma, 
or  stroma.  The  stroma  consists  of  two  parts,  an  external  or 
cortical  portion,  whitish  in  color,  and  an  internal  medullary 
or  vascular  zone,  reddish  in  color,  and  consisting  of  vessels 
elastic  fibres  and  connective  tissue  among  which  are  a 
number  of  non-striated  muscular  fibres.  The  external  por- 
tion consists  of  a  network  of  connective  tissue  in  which  th« 
Graafian  vesicles  are  ff-vnied.  There  are  also  a  large  num- 
ber of  nuclei  in  the  interstices.  The  Graafian  vesicles  or 
ovisacs,  exist  in  very  large  numbers  from  the  earliest  periods 
of  life,  and  in  all  stages  of  development.  They  vary  in  size 
from  a  pin's  head  to  a  pea,  and  contain  the  ova.  Each 
Graafian  vesicle  consists  of  an  ex- 
ternal vascular,  and  an  i^iternal 
serous  coat,  named  the  ovicapsule. 
The  internal  coat  is  lined  internal]}^ 
by  a  layer  of  nucleated  cells,  called 
the  menibrana  granulosa,  and 
within  this  is  situated  the  ovu7n. 


Fig.  127. 


The  cells  of  the  membrana  granu- 


Graaflaii  vesicle:  1,  stroma;  2, 
l)crit(meuin  ;  'A  and  4,  coats  of  the 
Graatian  vesicle ;  5,  membrana 
{rranulosa ;  0,  fluid  of  the  Graa- 
fian vesicle  ;  7,  discus  proligerus  ; 
8,  ovum. 


Fig.   128. 


losa  are  accumulated  in  large  num- 
bers around  the  ovum,  forming  a 
granular  zone,  the  cumulus,  discus  proligerus,  retinacula 
or  chalaza.  The  cavity  of  the  Graafian  vesicle  is  filled  with 
an  albuminous  fluid  in  which  granules  float. 

The  ovum  is  a  small  spherical  body,  about 
fjr-jj  of  an  inch  (.2  min)  in  diameter.  It  con- 
sists externally  of  a  transparent  envelope,  the 
zona  j)ellucida  or  vitelline  membrane,  and 
within  this  is  the  yolk  or  vitellus.  Imbedded 
in  the  substance  of  the  yolk  is  a  small  vesi- 
Ctdar  body,  the  germinal  vesicle,  and  within 
8potT2?gernfinai"v"s-  the  germinal  vesicle  is  the  germinal  spot. 
p'^efiucida  •*  5,'  'aiscub  The  latter  is  about  ^o^oo  of  ^^  ii^ch  (8mmm.) 
?Int|r™uies  or  cells,  in  diameter.  The  vitelline  membrane  is  a 
colorless  transparent  membrane,  which  appears  as  a  bright 

22 


380 


REPRODUCTION. 


fet 


I 


ring  with  a  dark  border  externally  and  internally,  and 
is  about  ^Aff  of  an  inch  (10  mmm.)  in  thickness.  The 
yolk  consists  of  granular  protoplasm,  the  smaller  granules 
resembling  pigment,  and  the  larger,  more  numerous  at  the 
periphery,  fat  globules.  The  germinal  vesicle  contaim  a 
watery  fluid  in  which  are  found  a  few  granules. 

At  the  approach  of  the  menstrual  period,  one  (or  probably 
more)  of  the  Graafian  vesicles  enlarges,  ai)proaches  the  sur- 
face of  the  ovary,  and  when  mature,  forms  a  small  projec- 
tion on  the  surface.  It  finally  bursts,  the  ovum  escapes, 
and  is  caught  by  the  fimbriated  extremity  of  the  Fallopian 
tube,  and  by  it  conducted  to  the  uterus. 

Corpus  Luteum. — When  the  Graafian  vesicle  has  ma- 
tured,and  is  about  to  burst  and  expel  the  ovum,  it  becomes 
highly  vascular  and  opaque,  and  its  coats  are  thickened  by  £>, 
glutinous  looking  substance.  As  the  ovum  escapes,  it  leaves 
behind  it  the  external  vascular  and  the  internal  serous  coats 
of  the  Graafian  vesicle,  the  cavity  of  which  is  immediatel}'' 
filled  with  a  bloody  fluid  which  soon  coagulates,  and  the 
cicatrix  presents  a  yellowish  appearance  ;  hence  it  has  been 
called  the  corpus  luteum  (Fig.  129).  After  a  short  timo  the 
Fiff^^.  coagulum   contracts,  and   the  mem- 

branes become  convoluted  and  hyper- 
trophied,  so  that  when  the  corpus 
luteum  is  divided  transversely,  about 
three  weeks  after  its  formation,  it  is 
seen  to  consist  of  a  central  firm  coa- 
gulum surrounded  by  a  convoluted 

Corpus  luteum,  natural  size,  ii      p  ij*   r  ii  i 

eight  days  after  conception:  a.    Wall  01  a  reddish  ycllOW  COlor. 

Corpora  lutea  are  divided  into  true 
and  false ;  the  former  are  found  only 
when  conception  has  taken  place  ;  the  latter  are  met  with 
in  the  unimpregnated  state.  They  are  both  produced  in 
the  same  way,  and  for  the  first  three  weeks  there  is  no  dis- 
tinction between  them  ;  but  the  true  corpus  luteum  becomes 


external  coat  of  tlie  ovary  ;  6, 
stroma  of  the  ovary;  c,  convo- 
luted wall  of  the  Graafian  folli 
cle  ;  d,  clot  of  blood. 


ACTION  OF  THE  OVIDUCTS. 


381 


mlly,  and 
less.  The 
r  granules 
•us  at  the 
jontaim  a 

r  probably 
2s  the  sur- 
all  projec- 
m  escapes, 
)  Fallopian 

ie  has  ma- 
it  becomes 
kened  by  &, 
3S,  it  leaves 
erous  coats 
rimediately 
>s,  and  the 
t  has  been 
t  time  the 
the  mem- 
and  hyper- 
the  coipus 
rsely,  about 
lation,  it  is 
il  firm  coa- 
convoluted 
olor. 

d  into  true, 
found  only 
'0  met  with 
)roduced  in 
e  is  no  dis- 
jm  becomes 


Fig.  130. 


larger  and  remains  longer  than  the  false,  in  consequence  of 
the  increased  vascularity  of  the  parts  after  impregnation. 

At  the  end  of  the  third  week  they 
each  measure  about  one-half  or  three- 
fourths  of  an  inch  in  diameter.  After 
this  the  false  corpus  luteum  begins 
to  diminish,  and  entirely  disappears 

in     the    course    of  about  two    months,      corpus  luteum.  natural  Mze  at 

while    the    true    increases    in    size,  nt^nll^r^he^^VryTrZlo: 
until     about      the     fourth      or     fifth   dofrdecoiorized';;o?;^ 
month,  and  then  gradually  declines  °JJ* Z*"^"  "i^*' "  t le corpus lute- 

until  after  parturition,  when  it  rapidly  disappears. 

Action  of  the  Oviducts. — In  the  human  subject  the 
oviducts  commence  by  a  wide  fringed  expansion — the 
fimbriated  extremity  of  the  Fallopian  tubes.  The  ovum,  in 
passing  through  the  Fallopian  tube  to  the  uterus,  absorbs  a 
certain  quantity  of  fluid,  increases  in  size,  and  if  impreg- 
nated soon  presents  a  number  of  minute  villi  on  its  surface 
which  give  it  a  shaggy  appearance.  This  is  called  the 
chorion. 

In  fowls,  as  the  ovum  leaves  the  ovary  it  enters  the  ovi- 
duct, and  in  passing  the  first  portion,  which  is  about  two 
inches  in  length,  it  ab-sorbs  fluid  and  becomes  more  flexible 
and  yielding.  In  the  second  portion,  which  is  about  nine 
inches  in  length,  the  mucous  membrane  is  thick  and  glan- 
dular. In  the  upper  part,  it  secretes  a  vi.scid  fluid  which 
surrounds  the  yolk  and  forms  a  gelatinous  deposit  around 
the  vitelline  membrane,  and  from  the  rotation  given  to  the 
egg  by  the  oviduct  the  two  ends  become  twisted  in  o])po.site 
directions  from  the  poles  of  the  egg  and  form  the  chalazoe. 
The  membrane  which  connects  the  chalazse,  is  called  the  cha- 
lazif erous  membrane.  In  the  rest  of  this  portion, an  albumin- 
ous secretion  is  poured  out  to  form  the  albumen  or  white  of 
the  egg.  In  the  third  division,  which  is  about  three  inches 
in  length,  a  material  is  poured  out  which  conden.ses  and 
forms    three  fibrous  membranes,  an  internal,  middle  and 


382 


REPRODUCTION. 


c 
c 

»!■> 


Ik: 

B 


■^v. 


external.  The  egg  then  passes  into  the  fourth  division, 
whicii  is  about  two  inchcH  long.  This  pours  out  a  secretion 
containing  calcareous  matter,  which  is  deposited  in  the 
meshes  of  the  external  membrane  of  the  egg,  forming  the 
shell.  After  the  expulsion  of  the  eg^,  evaporation  of  some 
of  the  watery  in^nedients  takes  ])lace  through  the  pores  of 
the  shell,  its  j)lacc  being  filled  with  air.  The  air  cavity  is 
situated  between  the  internal  and  middle  membranes,  at  the 
,  large  end  of  the  egg.  The  vitellus  is  the  essential  part  of 
the  egg,  the  white  simply  contributing  to  the  nourishmert 
of  the  chick  until  it  leaves  the  shell,  and  the  membranes 
and  shell  affording  the  protective  coverings. 

Development  of  the  Ovum. — After  the  ovum  is  im- 
pregnated a  remarkable  change  takes  })lacc,  which  is  known 
as  the  spontaneous  division  or  segmev  'atior  of  the  vitellus. 
A  furrow  first  shows  itself  sur/ounding  the  vitellus  in  a 
vertical  direction,  which  gradually  becomes  deeper  until  it 

Fig's,  131-4. 


has  divided  into  two  portions.  Each  of  these  portions  is 
again  subdivided  into  two,  and  the  four  segments  thus  pro- 
duced are  divided  into  sixteen,  and  sixteen  into  sixty-four, 
and  so  on,  until  the  whole  mass  has  assumed  a  mulberry  ap- 
pearance, and  is  finally  converted  into  "  vitelline  spheres  " 
or  "  true  animal  cells,"  which  adhering  together,  form  the 
bladodermic  membrane.  These  cells  are  also  sometimes 
called  the  primordial  or  primitive  cells,  or  germinal 
vesicles.  The  albuminous  matter  liquefies,  and  gradually 
passes  by  osmosis  through  the  vitelline  membrane  into  the 
interior  of  the  egg.  The  blastodermic  membrane  then 
divides  into  two  layers,  the  external  blastodermic  serous  or 


■ 


division, 
secretion 
ed  in  the 
ming  the 
a  of  some 
e  pores  of 
cavity  is 
les,  at  the 
ial  part  of 
irishmen  t 
lembranes 

m  is  im- 
1  is  known 
le  vitellus. 
jllus  in  a 
ir  until  it 


lortions  is 
thus  pro- 
dxty-four, 
[berry  op- 
spheres  " 
form  the 
sometimes 
germinal 
gradually 
!  into  the 
ane   then 
,  serous  or 


DEVELOPMENT  OF  THE   OVUM. 


383 


ani/mal  layer,  and  the  internal  hlastodei'mic,  mucous  or 
vegetative  layer,  both  of  which  are  composed  of  cells.  The 
former  produces  the  spinal  column  and  organs  of  animal 
life ;  the  latter  the  alimentary  canal  and  organs  of  vegetative 
life.  Up  to  this  stage,  the  process  is  the  same  in  all  animals, 
birds,  fishes,  reptiles  and  mammalia. 

The  simplest  form  of  development  is  seen  in  the  egg  of 
the  frog.  The  egg,  when  discharged  from  the  body  and 
fecundated,  is  deposited  in  the  water,  surrounded  by  a  layer 
of  albuminous  matter,  and  is  freely  exposed  to  the  light  and 
heat  of  the  sun.  The  first  sign  of  organization  is  the  thicken- 
ing and  condensation  of  the  external  blastodermic  mem- 
brane in  one  part,  foi  ming  an  elongated  oval  spot  with 
opaque  edges.     This  is  called  the  emhryonic  spot.     Enclosed 

Fi','.  i;wi. 


The  lm])rcj,'iiated  ovum  showing 
the  enihr.vonic  spot,  aieapullucida 
and  primitive  trace. 


Oommenclnvr  formation  of  the 
embryo;  a,  external  l)lasloder- 
raic  layer ;  b,  vitellus ;  c,  embryo. 


within  this  is  a  narrow  transparent  space,  the  area  pellucida, 
in  the  centre  of  which  is  a  longitudinal  line,  the  primitive 
trace.  On  each  side  of  the  primitive  trace  in  the  area 
pellucida,  the  blastodermic  membrane  rises  up  in  two  plates, 
called  the  dorsal  plates,  which  at  last  meet  and  enclose  a 
foramen,  the  spinal  canal,  in  which  nervous  matter  is  de- 
posited to  form  the  spinal  cord,  being  enlarged  anter'orly  to 
accommodate  the  brain.  At  the  same  time  the  external 
blastodermic  membrane  grows  outwards  and  downwards,  to 
form  the  abdominal  walls  which  embrace  the  internal  blasto- 
dermic  membrane   and  the  fluid  in   its  cavity.     Beneath 


384 


REPRODUCTION. 


\ 

In 
I 

\ 
\ 

•J' 


Diagram  of  a  scution  of  tlie  embryo  Hliowinjf 
the  formation  of  the  npine ;  a,  cpibloHt  :  h, 
hypoblast ;  c,  iiie.sol)la»t ;  d,  miirKin  of  tlie 
lamina  ih)rMaIis;  e,  medullary  i^roove  ;  (, 
chorda  dorxalis  or  notocliord ;  Xi  prhnilive 
or  protovertebra. 


the  spinal  canal  is  formed  a  cartilaginous  cord,  which  is 
called  the  chorda  doi'salis,  from  which  the  vertebrce  are 
subsequently  developed.     As  the  whole  mass  grows  rapidly, 

the  head  becomes  thick  and 
voluminous,  while  the  tail 
begins  to  project  baokwardfl, 
and  the  embryo  assumes  an 
elongated  form.  The  internal 
blastodermic  layer  forms  the 
alimentary  canal,  the  mouth 
and  anus  being  developed  by 
atro])hy  and  perforation  of  l,he  external  layer  of  the  blasto- 
dermic membrane  at  these  points  respectively.  The  young 
tadpole  then  ruptures  the  vitelline  membrane  and  escapes, 
after  which  the  extremities  are  developed  by  a  process  of 
budding  or  sprouting,  and  when  fully  formed,  the  tail  atro- 
phies and  disappears.  The  animal  at  first  breathes  by  gills  ; 
but  these  are  subsequently  replaced  by  the  lungs. 

In  the  development  of  the  chick  which  has  been  studied 
very  carefully  by  various  observers,  the  blastodermic  mem-, 
brane,  or  hlastoderm  divides  into  three  layers,  the  two  lay- 
ers already  referred  to  in  the  frog,  and  an  "  intermediate 
layer  "  or  mesoilast.  These  three  layers  are  designated  by 
.some,  the  epihlast,  mesoblast  or  middle  layer,  and  the  hypo- 
blast. The  epiblast  forms  the  epidermis  and  appendages, cere- 
bro-spinal  nerve  centres,  sensorial  epithelium  of  the  nt  se,eye, 
ear  etc.,  and  the  epithelium  of  the  mouth  and  sali  varj'  glands. 
From  the  mesoblast  is  formed  the  tissues  of  the  body,  con- 
nective, muscular  and  nervous  tissues,  vascular  and  genito- 
urinary systems,  and  digestive  canal  except  its  epithelium  ; 
and  from  the  hypoblast  is  developed  the  epithelium  of  the 
alimentary  canal  and  the  ducts  that  open  into  it,  and  also 
the  parenchyma  of  the  glands,  as  the  liver  and  pancreas.  In 
the  egg  of  the  fowl,  a  whitish  circular  spot  is  seen,  about  ^ 
of  an  inch  (5  mm)  in  diameter,  immediately  beneath  the 
vitelline  membrane,  the  cicatricula,  in  the  centre  of  which 


DEVELOPMENT  OF  THE  OVUM. 


385 


which  is 
ebrre  are 
8  rapidly, 
hick  and 

the  tail 
inkwardfl, 
mraes  an 
B  internal 
orrns  the 
le  mouth 
eloped  by 
lie  blasto- 
"he  young 
:1  escapes, 
process  of 

tail  atro- 
s  by  gills ; 

•n  studied 
mic  mem-. 

two  lay- 
ermediate 
;ynated  by 
the  hy-po- 
ages,cere- 
;  ncse.eye, 
r}'^  glands, 
jody,  con- 
tid  genito- 
lithelium  ; 
im  of  the 

and  also 
creas.  In 
n,  about  \ 
neath  the 
of  which 


is  the  germinal  vesicle.     When  the  egg  is  fecundated,  seg- 
mentation begins  in  the  cieatriculain  the  manner  already  de- 
scribed, until  the  blastoderm  comes  to  occupy  the  place  of  the 
cicatricula.      It  then  separates  into  the  three  layers  above 
mentioned,  in  which  certain  prominences  and  foldings  take 
place  which  mark  out  the  commencing  development  of  the 
difterent  parts  of  the  embryo,  as  the  "  headfold,"  "  tailfold," 
etc.,  (Fig.  138.)     On  each  side  of  the  primitive  trace  (Fig. 
135),  the  epiblast  rises  up  to  form  the  dorsal  plates  (laminae 
dorsales),  which  soon  meet  and  close  in  the  spinal  or  medul- 
lary groove,  and  form  a  canal  for  the  reception  of  the  spinal 
cord  and  brain  (Fig.  137,  d).     Beneath  this  canal  in  the 
me-soblast  is  formed  the  c/iorc/a  cZorsa^is  or  notochord,  which 
ultimately  becomes  the  spinal  column  ;  on  each  side  of  the 
chorda  dorsalis,  a  longitudinal  thickening  of  the  mesoblast 
takes  plact  from  which  is  formed  the  primitive  vertebrae 
(protovertebrie).     These  structures  form  the  bases  out   of 
which  the  spinal  column  and  muscles  are  afterwards  d  • 
veloped.     On  the  outer  side  of  the  primitive,  or  protover- 
tebrse,  the  mesoblast  splits  into  two  laminae,  one  joins  the 
epiblast  (fcomatopleure)  and  forms  the parietes  of  the  trimk, 
and  the  other  joins  the  hypoblast  (splanchnopleure)  and 
forms  the  alimentary  canal  and  other  parts.      The  general 
cavity  of  the  body  is  formed  by  downward  foldings  of  the 
blastoderm,   somewhat   resembling   the   formation   of  the 
nervous   canal  (Fig.  138).     These  downward   foldings  are 
called  the  visceral  plates.     In  the  frog  these  plates  close  in 
the  whole  of  the  vitellus. 

In  the  chick,  fish,  etc.,  the  internal  blastodermic  membrane 
is  divided  into  two  parts  by  a  constriction, one  of  which  forma 
the  intestinal  canal,  while  the  other,  remainingoutside,  forms 
the  umbilical  vesicle,  which  is  surrounded  by  a  portion  of 
the  external  blastodermic  membrane,  and  is  gradually  atro- 
phied as  development  proceeds. 

In  the  human  embryo  the  umbilical  vesicle  becomes  more 
completely  separated,  and  forms  a  cord  by  its  constriction, 


386 


REPRODUCTION. 


c 
c 

[ 

I* 

L 

I 


to 


at  the  distal  extremity  of  which  is  situated  the  vesicle, 
which  contains  a  clear  transparent  fluid  (Fig.  139,  g).  The 
umbilical  vesicle  may  continue  until  the  end  of  the  third 
month,  after  which  it  gradually  disappears  in  the  advancing 
develojiment  of  the  adjacent  parts  (Fig,  141). 

Formation  of  the  amnion  and  Allantois. — These 
are  two  accessory  organs  which  belong  to  the  higher  order 
of  animals,  and  their  development  has  been  carefully  studied 
in  the  chick.  The  amnion  is  formed  from  the  external 
layer  of  the  blastodermic  membrane,  and  the  allantois  from 
the  internal  ;  the  former  encloses  a  cavity  or  sac  containing 
fluid  in  which  the  foetus  floats ;  the  latter  is  a  vascular 
structure  destined  to  bring  the  blood  of  the  embryo  to  the 

Fiff.  i;!8  Fis-  i;^i>- 


Diajjfriun  of  tlio  formation  of  the  aiunioii  and  allantois :— rt,  vitelline  membrane  covered 
with  the  villi  of  the  chorion  ;  h,  folds  of  the  amnion  suircuuling  the  emliryo  ;  e,  point  of 
meetinf;  of  amniotic  folds  ;  </,  outer  layer  of  the  amniotic  fold  ;  e,  inner  do.;  ./;  amniotic 
cavity  ;  g,  umbilical  vesicle  ;  /i,  allantois ;  i,  cavity  of  the  intestine  ;  ,fc',  space  between  the 
two  layers  of  the  amnion  ;  o,  situation  of  the  heart  and  vessels. 

external  sources  of  nutrition  and  atmospheric  influence. 
These  are  not  necessary  to  the  development  of  the  egg  of 
the  frog  and  fish,  since  absorption  can  readily  take  place 
through  the  vitelline  membrane,  from  the  media  by  which 
they  are  surrounded. 

The  avinion  is  first  formed  ;  this  takes  place  by  foldings 
of  the  external  blastodermic  membrane,  which  pass  upwards 
from  the  abdominal  surface  on  all  sides  of  the  embryo,  until 
they  meet  and  fuse  at  a  point  over  the  back  which  is  called 


THE  AMNION  AND  ALLANTOIS. 


387 


be  vesicle, 
,g).  The 
the  third 
idvancinsr 

s. — These 
her  order 
ly  studied 

external 
itois  from 
ontaiiiing 

vascular 
^o  to  the 


raiie  covered 

' ;  c,  point  of 

;  /;  amniotic 

between  the 


ifluence. 
egg  of 
ce  place 
y  which 

foldings 
ipwards 
^o,  until 
is  called 


Fig.  140. 


the  amniotic  uvibilicus  (Fig.  1 38, c).  Atrophy  and  separation 
then  take  place  at  this  point,  the  inner  layer  of  the  fold  form- 
ing the  amnion ;  the  outer,  blending  with  the  vitelline  mem- 
brane, and  forming  the  external  investing  membrane  of  the 
ovum.  A  shut  sac  is  thus  formed  between  the  amnion  and  the 
foetus  called  the  amniotic  cavity,  which  is  filled  with  a  clear 
fluid — the  liquor  amnii  (Fig.  139,/). 

About  this  time  the  allantois  commences  as  a  prolonga- 
tion or  diverticulum  from  the  posterior  part  of  the  intestinal 
canal,  and  follows  the  course  of  the  anmiotic  fold  which 
preceded  it,  lying  between  its  two  layers  (Fig.  139,  h).  It 
gradually  increases  in  size  until  it 
covers  the  body  of  the  embryo,  to- 
gether with  the  amnion ;  it  then 
mtets  and  fuses  over  the  back  as  did 
the  amniotic  folds  (Fig.  140).  It 
therefore  lines  the  whole  internal 
sui'face  of  the  investing  membrane 
of  the  ovum  with  a  flattened  vascu- 
lar sac,  the  vessels  of  which  come 
from  the  interior  of  the  body  of  the 
embryo.  The  cavity  of  the  allantois     i"ormationottiioaiianto;j:-«,in. 

''  ''  ner  layur  of  amnion  ;((,  outer  layer 

is  continuous  with  the  cavity  of  the    of  amnion  ;  c,  amniotic  oavi\v;(i, 

•^  vessels  of  the  allantois ;  e,  umbili- 

intestines.  The  umbilical  vesicle  is  *^'''  vesido. 
situated  between  the  amnion  and  allantois.  In  the  chick 
the  allantois  comes  immediately  in  contact  with  the  shell 
membrane,  taking  the  place  of  the  albumen  which  has  been 
liquefied  and  absorbed ;  and  through  the  pores  of  the  shell 
an  interchange  of  gases  takes  place,  oxygen  being  absorbed 
from  the  air,  and  carbonic  acid  exhaled  from  the  blood-ves- 
sels of  the  allantois.  It  will  be  seen,  therefore,  that  a  true 
respiration  takes  place  by  means  of  the  allantois  throuf.h 
the  external  covering.  When  the  chick  arrives  at  maturity, 
it  breaks  open  the  shell  and  escapes  from  its  confinement ; 
the  allantoic  vessels  are  torn  ofl'  at  the  umbilicus,  and  the 
allantois  remains  behind  in  the  abandoned  egg  shell. 


S88 


REPRODUCTION. 


c 

I 

V 

[ 


in; 
•to 


Formation  of  the  Chorion.  —  In  the  human  embryo 
the  obliteration  of  the  cavity  of  the  allantois  takes  place 
very  early,  so  that  it  does  not  enclose  a  cavity,  but  fuses 
together,  and  uniting  with  the  outer  fold  of  the  amnion  and 
the  vitelline  membrane,  constitutes  the  chorion.  Hence 
there  aro  two  membranes  in  the  foetus,  the  amnion  and  the 
chomon,  and  the  umbilical  vesicle  is  situated  between  the 
two.  The  chorion  in  the  human  subject  is  identical  with 
the  allantois  of  the  lower  animals,  its  chief  peculiarity 
being  that  its  opposite  surfaces  are  adherent  instead  of 
enclosing  a  cavity.  The  next  peculiarity  of  the  chorion 
is  that  it  becomes  shaggy,  owing  to  the  numbor  of  minute 
villi  or  "  villosities"  which  are  found  on  its  surface  (Fig. 
139).  The  villi  may  be  distinctly  seen  as  .soon  as  the  ovum 
has  reached  the  uterine  cavity,  even  when  it  is  still  very 
Bmall.  They  continue  to  grow  and  elongate,  and  divide  into 
a  number  of  branches  by  the  process  of  sprouting,  each  fila- 
ment terminating  in  a  rounded  extremity.  The  whole  tuft 
bears  a  certain  resemblance  to  some  varieties  of  seaweed. 
The  vessels  of  the  chorion  pass  into  the  villosities,  forming 
Fig.  141.  loops  like  the  vessels  in  the  villii 

of  the  small  intestine.  The  villi  of 
the  chorion  therefore  bear  a  slight 
reseTTiblance  to  those  of  the  small 
|i  intestine ;  but  are  unlike  any  other 
structure  of  the  body,  and  their 
presence  in  the  uterus  or  its  dis- 
charges may  be  considered  as  a 
proof  of  pregnancy. 
The  iiuinan  ovum  .it  about  the      The  villi  are  the  organs  through 

third  month,  slioA'ing  the  enliirge-       ...  .,  ,.  ^^     ^   n 

ment  of  the  cavif,  „r  ^i,^  amnion,  wliich  nourishment  IS  suppiicd  irom 

the  foruiaiion  of  the  placental  por-       .  ,  .  .         . 

tionof  the  chorion,  the  commencing  Without,  at  thlS    StagC  ot   eXlSteUCC. 

fovniation  of  the  umbilical  cord,  and  -,        n       i 

the  atrophy  of  the  umbilical  vesicle.  At    aboUt    tllC    CUd    Of     the     SCCOUd 

month  the  villi  become  atrophied,  except  at  the  part  which 
€oriecj|jonds  with  the  insertion  of  the  foetal  vessels,  and  the 
cliorion  becomes  partly  bald  (Fig.  141).     Those  villi  which 


PREPARATION  OF  THE  UTERUS. 


389 


lan  embryo 
bakes  place 
',  but  fuses 
imnion  and 
?«..     Hence 
\on  and  the 
atween  the 
atical  with 
peculiarity 
instead  of 
he  chorion 
of  minute 
irface  (Fig. 
!  the  ovum 
!  still  very 
divide  into 
\,  each  fila- 
whole  tuft 
f  seaweed, 
js,  forming 
1  the  villii 
'he  villi  of 
-r  a  slight 
the  small 
any  other 
and  their 
)r  its  dis- 
jred   as  a 

3  through 
plied  from 
existence, 
le  second 
art  which 
;,  and  the 
illi  which 


remain,  continue  to  grow,  and  ultimately  form  the  placenta, 
which  attaches  itself  to  the  uterus  (Fig.  142). 

Preparation  of  the  Uterus  to  Receive  the  Ovum. 
— As  the  impregnated  ovum  is  about  to  descend  into  the 
cavity  of  the  uterus,  the  mucous  membrane  becomes  gi'eatly 

Fig.  142. 


Vertical  section  of  the  womb,  containing  a  developed  ovum  ;  a,  neck,  filled  with  a  gel- 
atinous plug  ;  66,  orifice  of  the  Fallopian  tubes  ;  cc,  decidua  ve  'a  ;  d,  uterine  cavity,  almost 
entirely  filled  with  the  ovum  ;  ec,  decidua  vera  continuous  with  the  decidua  reflexa  ;  /, 
placenta ;  g,  allantois ;  h,  umbilical  vesicle  and  its  pedicle  in  the  umbilical  cord ;  i,  am- 
nion; k,  decidua  reflexa  and  chorion. 

hypertrophied,  tumefied, and  vascular, and  projects  in  rounded 
eminences  into  the  uterine  cavity.  The  tubules  or  follicles 
are  elongated,  and  enlarged  so  that  their  open  mouths  may 
be  seen  with  the  naked  eye.  The  hypertrophied  mucous 
membrane  is  called  the  decidua  vera.  When  the  ovum 
reaches  the  uterus  it  insinuates  itself  between  the  opposite 
surfaces  of  the  mucous  membrane,  and  becomes  lodged  in 


390 


REPRODUCTION. 


c 

[ 

\ 

% 

I 

HE 

I 

5;. 


one  of  the  depressions  between  the  projecting  eminences  of 
the  decidua,  where  it  subsequently  becomes  fixed.  At  this 
point  a  rapid  development  of  the  mucous  membrane  takes 
place,  and  a  folding  or  prolongation  of  the  decidua  surrounds 
and  envelopes  the  ovum,  called  the  decidua  reflexa. 

It  was  formerly  supposed  that  the  decidua  was  an  entirely 
new  product,  thrown  out  by  exudation  from  the  surface  of 
the  uterus,  similar  to  the  inflammatory  exudation  of  croup, 
etc.,  which  surronndod  the  whole  internal  surface  of  the 
uterus,  and  was  called  the  decidua  vera.  As  the  ovum 
passed  from  the  Fallopian  tube  into  the  uterus  it  pushed 
before  it  a  folding  of  the  decidua  vera,  which  formed  the 
decidua.  reflexa.  The  closure  of  this  folding  behind  the 
ovum,  was  called  the  decidua  serotina.  This  was  the  theory 
of  William  Hunter.  It  is  iio^'  known  to  be  no  other  than 
the  mucous  membrane  itself,  very  much  thickened  and 
hypertrophied. 

Formation  of  the  Placenta. — The  placenta  is  formed 
partly  by  the  vascular  tufts  of  the  chorion,  and  partly  by 
the  hypertrophied  mucous  membrane  to  which  they  are 
connected.  About  the  commencement  of  the  third  month, 
the  villi  which  avo  uestined  to  enter  into  the  formation  of 
the  placenta  coj.Hnue  to  elongate,  and  penetrate  or  are 
pushed  into  the  I'o  les  of  the  mucous  membrane,  (like  the 
fingers  into  a  glove),  which  are  enlarged  for  their  reception. 
The  growth  of  the  villi  and  that  of  the  follicles  go  on  sim- 
ultaneously, and  keep  pace  with  each  other.  The  capillaries 
of  the  villi  are  enlarged  and  become  tortuous,  and  those  on 
the  exterior  of  the  follicles  enlarge  excessively  and  become 
dilated  into  wide  sinuses,  wliich  are  filled  with  blood  derived 
from  the  arteries  of  the  uterus,  so  that  two  membranes  inter- 
vene between  the  capillaries  of  the  villi  and  the  sinuses  of 
the  uterus,  viz.,  the  covering  of  the  villi  and  the  lining  mem- 
brane of  the  follicles.  These  afterwards  fuse  together  and 
blend  with  the  walls  of  the  capillaries  on  the  one  hand,  and 
the  walls  of  the  sinuses  on  the  other.     The  tufts  of  the  villi 


PLACENTA  AND  UMBILICAL  CORD. 


391 


inences  of 

At  this 

me  takes 

mrrounds 

X. 

1  entirely 
iurface  of 
of  croup, 
3e  of  the 
.he  ovum 
it  pushed 
rmed  the 
hind  the 
le  theory 
ther  than 
sned   and 

is  formed 
Dartly  by 
they  are 
d  month, 
nation  of 
e  or  are 
(like  the 
eception. 

on  sim- 
ipillaries 
those  on 

become 
1  derived 
es  inter- 
inuses  of 
ng  mem- 
/her  and 
and,  and 
the  villi 


are  prolonged  into  the  sinuses,  pushing  before  them  the  walls, 
and  are  every wheie  bathed  with  the  blood  of  the  mother. 
The  process  of  osmosis  takes  place  through  the  thin  fused 
membrane,  there  being  no  direct  communication  between 
the  foetal  and  maternal  vessels.  The  placenta  is  fully  formed 
about  the  commcmcement  of  Utj  fourth  month,  and  consti- 
tutes the  channel  through  which  nourishment  is  conveyed 
from  the  mother  to   the  foetus.     The   nutritive   material 
passes  from  the  blood  of  the  mother  through  the  interven- 
ing membrane  by  osmosis,  and  enters  the  blood  of  the  foetus. 
Besides,  the  placenta  is  an  organ  of  exhalation  as  well  as  of 
absorption.     The  impurities  circulating  in  the  blood  of  the 
foetus  are  here  discharged  into  the  maternal  vessels,  to  be 
removed  by  the  excretory  organs  of  the  mother ;  so  that  the 
placenta  may  be  said  to  fulfil  the  double  office  of  the  lungs 
and  stomach  in  the  foetus.     In  consequence  of  the  intimate 
relation  existing  between  the  mother  and  the  foetus,  there 
is  no  doubt  that  nervous  impressions  experienced  by  the 
former,  such  as  fear,  anger,  disgust,  etc.,  which  disturb  the 
circulation,  may  occasion    deformities   and   deficiencies  of 
various  kinds,  nsevi,  warts,  etc.,  in  the  latter.     The  circula- 
tion in  the  foetus  has  been  already  described  (p.  227). 

Umbilical  Cord  and  Amniotic  Fluid. — The  umbilical 
cord,  or  funis,  is  the  connecting  link  between  the  foetus  and 
placenta.  In  early  life  it  is  very  short,  and  consists  of  that 
portion  of  the  allantois  or  chorion  next  the  abdomen.  The 
umbilical  vesicle  is  situated  between  the  amnion  and  cho- 
rion, the  rest  of  the  space  being  filled  with  a  gelatinous 
fluid.  The  amnion  continues  to  expand,  the  quantity  of 
liquor  amnii  increases,  and  about  the  beginning  of  the  fifth 
month  the  amnion  comes  in  contact  with  the  chorion,  the 
umbilical  vesicle  and  gelatinous  fluid  gradually  disappearing. 
The  umbilical  cord  at  the  same  time  elongates  in  proportion 
to  the  increasing  size  of  the  amnion,  and  towards  the  close 
of  gestation  the  amnion  and  chorion  blend  together  and  con- 
stitute what  is  commonly  called  the  "  membranes."    As  the 


392 


REPRODUCTION. 


»j 


«^ 


,i 


Fiif.  143. 


cord  lengthens  it  twists  from  right  co  left.  It  consists  of 
the  two  umbilical  arteries,  the  umbilical  vein,  the  urachus, 
and  the  remains  of  the  umbilical  vesicle,  imbedded  in  a 
gelatinous  material  (Whartonian  jelly)  and  surrounded  by 
a  folding  of  the  amnion.  The  cord  at  full  term  varies  in 
length  from  one  to  three  feet. 

Parturition. — The  discharge  of  the  foetus  is  termed  par- 
turition. This  is  effected  by  the  contraction  of  the  muscular 
fibres  of  the  uterus,  resisted  in  the  second  stage  by  the 
contraction  of  the  diaphragm,  abdominal,  and  other  muscles 
of  the  body.  The  placenta  is  separated  from  its  attachment 
to  the  inner  surface  of  the  uterus,  during  which  the  sinuses 
are  lacerated  and  a  certain  amount  of  hemorrhage  occurs, 
w^hich,  however,  is  soon  arrested  by  the  contraction  of  the 
uterus  and  consequent  closure  of  the  mouths  of  the  vessels 
leading  to  the  sinuses. 

After  parturition  the  utorus  under- 
goes the  process  of  involution.  This 
consists  of  a  diminution  in  the  size  of 
the  uterus,  and  a  change  in  the  appear- 
ance of  the  muscular  fibre  cells.  The 
muscular  fibres  of  the  uterus,  during 
gestation,  are  very  much  increased  in 
size,  and  granular  in  appearance.  After 
parturition  they  appear  to  undergo  a 
fatty  degeneration  ;  fat  globules  make 
their  appearance  in  the  interior  of  the 
Muscular  fibre  cells  of  the  muscular  fibre  ccUs  :  the  tissue  becomes 

uterus  two  weeks  after  par-  .  n         i  i      i    • 

turition.  soit  and  IS  gradually  absorbed,  its  place 

being  supplied  by  new  cell  fibres. 

GENERAL  DEVELOPMENT  OF  THE  EMBRYO. 

The  development  of  certain  parts  of  the  body  from  the 
blastoderm,  has  been  already  casually  referred  to.  The 
several  organs,  and  systems  of  organs  will  now  be  considered 
in  their  order  of  succession. 


consists  of 
le  urachus, 
jdded  in  a 
ounded  by 
a  varies  in 

termed  par- 
te muscular 
age  by  tbe 
her  muscles 
attachment 
the  sinuses 
lase  occurs, 
ction  of  the 
[*  the  vessels 

iorus  under- 
ition.     This 
L  the  size  of 
the  appear- 
cells.     The 
?rus,  during 
increased  in 
ranee.  After 
3  undergo  a 
obules  make 
terior  of  the 
ssue  becomes 
■bed,  its  place 


RYO. 

lody  from  the 
red  to.  The 
be  considered 


DEVELOPMENT  OF  THE  EMBRYO. 


395 


Development  of  the  Spine,  Cranium  and  Nervous 
System. — The  epiblast  as  has  been  already  stated,  rises  up 
in  the  form  of  plates,  and  encloses  the  medullary  or  spinal 
canal  (Fig.  137).     Beneath  this  in  the  mesoblast  is  formed 
the  chorda  dorsalis,  or  notochord,  and  at  each  side  the  proto- 
vertebree  which  increase  in  size  and  grow  up  around  the 
notochord  and  form  the  spine.     The  spinal  canal  becomes 
enlarged  an^eriorly,  corresponding  to  the  brain,  and  termi- 
nates by  a  pointed  extremity.     The  cranium  is  developed 
from  the  proto vertebras,  surrounding  the  upper  extremity 
of  the  chorda  dorsalis.     At  the  same  time  a  growth  of  ner- 
vous matter  takes  place  in  the  interior  of  the  canal.     At  first 
the  canal  has  an  oval  shape  on  section,  and   presents   an 
elongated  slit,  but  presently  the  opposite  sides  unite  in  the 
centre,    forming    the    gray    commissure    and       Fig.  i44. 
dividing  it  into  an  anterior  and  posterior  por-  I 
tion  ;  the  former  becomes  the  central  canal,  and 
the  latter  .^orms  the  posterior  fissure.     The  an- 
terior fissure  is  formed  by  an  inward  folding  of 
the  anterior  part.     At  this  stage  the  cord  con- 
sists chiefly  of  gray  matter.     White  matter  is 
now  developed  from  the  cells  of  the  mesoblast, 
and  covers  the  outer  surface  dipping  into  the 
bottoms   of    the    fissures   to    form   the    com- 
missures.    The  anterior  bulbous  enlargement, 
or  brain,   separates    into    three  portions,  the    tuc  spine  at  an 

7        7  .7  ,       •  .7  11  7  early  Off  e  showing' 

cerebral    vesicLes,   anterior,    middle    and   pos-  tiie  anterior  aiia- 

.  „  1  •    1       .1  i'if-  L  J.-  „  tation  and  proto- 

terior,  from  which   the  dmerent  portions    of  vertebrae ;  i,  2,  s, 

-  7  7        mi  ,       •  anterior,  middle, 

the  encephalon  are  oeveloped.     Ihe  anterior,  and  posterior  ee- 

,.7  7  •17-7        rebral  vesicles ;  a, 

forms  the   hemispheres  and  optic  thalami,  the  slight  Battening 

*■  *■  of    the    anterior 

middle,  the  corpora  quadrigemina,  and  the  pos-  vesicle;  b,  proto- 

'  r-  1  D  '  1  vcrtebnc ;  c,  lum- 

terior,  the  cerebellum  and  medulla  oblongata,  bar  enlargement : 

'  o  o,    optic    vesicle 

At  this  period  the  size  of  the  different  parts  of  (Longet). 
the  encephalon  is  different  from  the    same  organs  in  the 
adult ;  e.  g.  the  hemispheres  are  only  slightly  larger  than 
the  corpora  quadrigemina,  and   the  cerebellum  is  smaller 


394 


DEVELOPMENT  OF  THE  EMBRYO. 


c 
c 

[ 

•I 

t 


r    ! 


Hi 

t«». 


!      I 
I 


!   i 


than  the  medulla  oblongata.  As  development  pioceeds, 
however,  the  relative  size  of  the  different  parts  soon  changes, 
convolutions  begin  to  make  their  appearance,  and  the 
hemispheres  are  divided  by  the  longitudinal  fissure. 

Development  of  the  Face. — As  the  cerebral  ex- 
tremity of  the  foetus  beccnes  developed,  i<".  bends 
forwards  upon  its  axis  and  forms  the  cerebral  and 
frontal  ])romiiiences  and  four  depressions,  the  cervical  fis- 
sures. Between  the  fissures  are  four  foldings  or  arches.called 
the  visceral  or  'pharyngcdl  arches,  in  which  are  developed 
the  bones  of  the  face.  Between  the  first  pharyngeal  arch  and 
the  frontal  prominences,  is  the  opening  of  the  n:outh.  The 
first  pharyngeal  arch  divides  into  a  superior  and  in  inferior 
protuberance  on  each  side;  the  latter  unites  very  fcoon  with 
its  fellow  of  the  opposite  side  to  form  the  lower  ja\f-,  The 
superior  protuberances  which  form  the  upper  jaw  ui  jj;e  in 
the  median  line,  with  the  fronto-nasal  or  intermax|'flary 
process.  The  growth  of  these  parts  diminishes  the  siz(.*<of  the 
oral  cavity;  a  lamella  grows  in  wan  s  from 
the  superior  maxillary  tuberosity,  joins 
the  one  from  the  opposite  side  and  forms  the 
palatine  arch.  If  from  any  cause,  the 
superior  maxillary  and  intermaxillary  pro- 
cesses fail  to  unite  with  each  other,  hare-lip 
or  cleft  palate,  or  both,  are  the  result.  This 
serves  also  to  explain  why  hare-lip  is  always 
on  either  side  of  the  median  line,  single  or 
double;  in  the  latter  case  the  intermaxillary 
process  which  contains  the  incisor  teeth  is 


Fig.   145. 


Head  of  a  human 
foetus  at  the  5th  week  ; 
1,  frontal  prominen- 
ces ;  2,   cerebral  pro- 

Sproce-ss; /lateral  frequently  detached  from  the  superior  max 


KuplrC'SZl;  ilia,  and  is  adherent  to  the  nose.  Cleft  palate 
rearT&eT'''"'  ^^  causcd  by  a  deficiency  in  the  union  of  the 
the  lamellae  which  form  the  palatine  arch.  The  soft  palate 
may  be  cleft  also.  The  second  pharyngeal  arch  forms  the 
stapes,  stapedius  muscle,  pyramid,  styloid  process,  styloid 
ligaments  and  the  lesser  cornu  of  the  hyoid  bone ;  from  the 


proceeds, 
I  changes, 
and   the 
re. 

bral  ex- 
i<-.  bends 
3ral  and 
i-vical  fis- 
hes, called 
ieveloped 
I  arch  and 
ith.  The 
in  inferior 
sOon  with 
a\-,  The 
r  ui  jj:e  in 


max" 
siz':*of  the 
irrs  from 
ty,    joins 
forms  the 
ause,   the 
lary  pro- 
hare-lip 
It.     This 
is  always 
single  or 
naxillary 
teeth  is 
lor  m  ax- 
eft  palate 
on  of  the 
ft  palate 
orms  the 
I,  styloid 
from  the 


DE  VELOPME.\r  OF  THE  E  YE,  EAR  AND  NOSE.     395 

third  is  foi'nied  the  greater  cornu  and  body  of  the  hyoid 
bone  ;  and  from  the  fourth,  the  soft  parts  of^the  neck.  The 
cervical  fissures  all  disappear  in  a  short  time  except  the 
first,  which  forms  the  meatus  auditorius,  Eustachian  tube 
and  tympanic  cavity. 

Devf:lopment  of  the  Eye,  Ear  and  Nose. — The  eye 
is  formed  fiom  the  priniaiy  optic  vesicle,  an  outgrowth  from 
the  first  cerebral  vesicle  (Fig.  145.)  It  is  at  first  an  open 
cavity  comniunicating  by  a  hollow  stalk  with  the  general 
cerebral  cavity,  but  as  development  proceeds  it  is  filled  up 
and  becomes  the  optic  nerve.  The  lens  is  formed  by  a 
thickening  of  the  epidermic  layer,  and  is  received  into  a  de- 
pression in  the  primary  optic  vesicle.  After  a  time  a 
secondary  cavity  is  formed  behind  the  one  for  the  lens,  in 
which  the  vitreous  humor  is  secreted.  The  lens  is  at  first 
surrounded  by  a  vascular  capsule,  connected  with  the  arteria 
centralis  retinae,  and  forms  the  membrana  pupillaris.  Ves- 
sels pass  into  the  ball  and  form  the  choroid  coat.  The  epi- 
thelium of  the  cornea  is  developed  from  the  epiblast,  and 
the  cornea  and  the  sclerotic  are  dcv  eloped  from  the  meso- 
biast.  The  iris  is  formed  from  a  projection  of  the 
choroid.  The  pupil  is  at  first  closed  by  the  membrana 
pupillaris,  but  it  disappears  in  the  human  foetus  about  the 
seventh  month.  The  ear  is  developed  in  the  form  of  a 
vesicle,  the  primitive  auditory  vesicle,  on  -'  j  outside  of  the 
third  cerebral  vesicle  over  the  second  pharyngeal  arch  (Fig, 
146,  8).  The  cavity  of  the  vesicle  forms  the  internal  ear, 
and  the  auditory  nerve  is  formed  from  the  mesoblast  which 
unites  the  cerebral  with  the  auditory  vesicle.  The  middle 
ear  and  Eustachian  tube  are  formed  from  the  first  pharyn- 
geal fisiure,  and  the  tympanum  from  a  membrane  stretched 
across  the  fissure.  The  pinna  is  formed  from  the  soft  parts 
of  the  first  i)haryngeal  arch,  and  the  ossicles  from  the  second 
pharyngeal  arch.  The  nose  arises  from  a  depression  in  the 
epiblast  at  each  side  of  the  fronto-nasal  process,  the  olfactory 
fossoi.  These  deepen  except  at  the  lower  part  where  they 
23 


306 


REPRODUCTION. 


c 


\ 

\ 

a, 

I 
ft- 

^•■ 
•«> 
tn 


load  by  the  olfactory  groove  into  the  cavity  of  the  mouth. 
After  the  formation  of  the  palatine  arches,  this  cavity  is 
divided  into  two  parts ;  the  lower  forms  the  mouth ;  the 
upper,  divided  by  a  septum,  the  nose.  The  olfactory  nerve 
is  derived  from  a  prolongation  of  the  anterior  cerebral 
vesicle. 

Fl(f.  146. 


Area  vasculosa  of  an  embryo,  ventral  surfauu.  1,  Terminal  sinus.  2,  Omjihalci-mesen- 
teric  vein.  3,  Its  posterior  branch.  4,  Heart  in  the  form  of  an  S.  .">,  Primitive  aorta,  or 
posterior  vertebral  arteries.    C,  Omphalo-inesenteric  arteries. — Binchvff. 

Development  of  the  Extremities.  —  The  upper  and 
lower  limbs  are  formed  as  buds  from  the  anterior  and  pos- 
terior part  of  the  embryo,  by  a  projection  of  the  somato- 
pleure  covered  by  the  epiblast.  The  division  of  the  extremity 
of  these  buds  into  fingers  and|toes,  which  have  a  webbed 
appearance,  takes  place  at  an  early  period,  and  soon  after,  a 
constriction  or  groove  marks  the  situation  of  the  wrist-joint. 
As  growth  proceeds  another  groove  shows  itself, at  the  elbows 


be  mouth, 
cavity  is 
louth ;  the 
ory  iiervo 
■   cerebral 


nipluild-niesen- 
nitive  aorta,  or 


ippor  and 
•  and  pos- 
e  somato- 
extremity 
a  webbed 
on  after,  a 
vrist-joint. 
the  elbows 


DE  VELOPMENT  OF  THE  VA SCULA  R  S  YS  TEM.      397 

and  knees.    In  all  animals,  the  anterior  extremities  precede 
the  formation  of  the  posterior. 

Development  of  the  Vascular  System. — The  vascular 
system  assumes  three  different  forms  during  different  periods 
of  life,  viz.,  the  vitelline,  placental,  and  complete.  The  vitel- 
line circulation  commences  at  a  very  early  period  in  the 
chick,  and  consists  of  a  number  of  vessels  which  ramify  over 
the  surface  external  to  the  embryo,  and  form  a  plexus,  the 
"  area  vasculosa."  The  vessels  are  formed  from  the  cells  of 
the  mesoblast,  which  become  elongated,  or  branched,  unite 
with  each  other  and  become  liollowed  out  to  form  the  capil- 
lary walls  (p.  222).  The  blood  corpuscles  are  formed  from 
the  nuclei  of  these  cells.  The  function  of  this  structure  is 
to  absorb  the  nutrient  material  from  the  vitellus.  About 
this  time  the  heart  begins  to  make  its  appearance.  This 
organ  and  the  larger  blood-vessels  are  formod  on  the  same 
plan.  Masses  of  embryonic  cells  of  the  splanchnopleurc  are 
arranged  in  the  position,  form  and  size  of  the  develoi)iiig 
structures;  the  external  layers  of  cells  are  converted  into 
the  walls  of  the  organs  and  the  internal  form  the  first  blood 
corpuscles  (p.  174<).  The  heart  may  now  be  seen  as  a  minute 
red  pulsating  point,  even  before  the  muscular  fibres  have 
been  formed  ;  this  is  the  "  punctum  saliens"  of  Harvey.  The 
heart  is  at  first  tubular  in  form,  and  receives  posteriorly  the 
two  omphalo-mesenteric  veins,  and  opens  anteriorly  into  the 
primitive  aorta,  which  divides  into  two  vessels^  '''''''  ^*^- 
the  vertebral  arteries.  These  form  a  series  of 
arches,  and  give  off  the  two  omphalo-mesenteric 
arteries  to  the  area  vasculosa.  It  then  becomes 
curved  or  bent  upon  itself  like  the  letter  S  or  a 
horse  shoe,  and  partly  divided  by  constrictions 
into  three  cavities.  The  one  corresponding  with  jayonncubation 
the  arterial  end,  is  t^^e  bulbus  arteriosus ;  the  .rt'he'luricieTs,' 
one  at  the  venous  end,  the  auricle ;  and  the  one  the  bulbus'artt- 
inthe  middle  is  the  ventdcle,  which  becomes  ~-2'''«"«i'- 
more  rapidly  developed  uhan  the  others.     In  some  animals-'. 


Heart    of    the 


398 


REPRODUCTION. 


r 


!    I 


as  tho  Amphibia,  this  form  remains,  no  other  division  by 
se|)ta  takinj^  place  ;  but  in  tho  liij^her  animals  ami  man,  both 
auricle  and  ventricle  are  subdivided  by  septa,  and  the  bul- 
bus  arteriosus  disappeais  in  the  ventricles. 

In  man  and  the  higher  animals  in  which  tho  vitellus  is 
small,  the  vitelline  form  of  circulation  f^oon  disappears,  and 
is  replaced  by  the  pldcoital  or  allantoic  circulation.  Tho 
two  omphalo-mesenteric  arteries  become  blended  into  one 
artery,  and  the  correspondin<^  veins  into  one  vein.  They  are 
called  omphalo-mesenteric  arteries  because  they  supply  in 
part  the  "  omphalos"  or  umbilicid  vesicle,  and  j)artly  the 
mesentery  and  intestine.  After  a  time  the  umbilical  vesi- 
cle and  its  vessels  diminish,  the  mesenteric  vesselj  increase, 
and  the  allantois  grows  out  from  the  posterior  part  of  the 
intestinal  cavity,  carrying  with  it  tho  allantoic  or  placental 
vessels.  There  are  two  uinhilical  arteries  and  at  first  two 
corresponding  veins,  but  after  a  tim-^  one  of  the  veins  dis- 
appears, and  the  whole  of  the  blood  is  returned  from  the 
placenta  by  one  vein. 

The  complete  circulation  takes  the  place  of  the  placental 
circulation,  which  is  abruptly  terminated  by  the  separation 
of  the  placenta  at  birth.  This  transition  is  more  abrupt 
than  the  preceding ;  but  has  been  duly  provided  for  by  the 
gradual  development  of  the  necessary  organs. 

The  blood  vessels  first  commence  to  form,  as  previously 
stated,  in  the  area  vasculosa  external  to  the  body  of  the 
embr^'o.  The  first  aortic  arch  is  formed  by  the  division  of  the 
primitive  aorta  into  two  branches,  which  arch  backwards, 
and,  after  descending,  unite  into  one  vessel  in  front  of  the 
vertebral  column  (Fig.  148).  Other  pairs  of  arches  are 
formed  in  succession  behind  the  first,  to  the  number  of  five. 
These  are  not  all  to  be  seen  at  the  same  time,  for  as  some 
develope,  others  disap])ear.  In  fishes  they  all  persist  thiough 
life  and  form  the  distribution  as  seen  in  the  gills.  In  man 
and  the  higher  animals,  the  anterior  ones  disappear  and 
the  posterior  ones  become  transformed  into  the  carotids  (5  ), 


visi(Ui  by 
iiinn,  both 
(1  the  biil- 

vitulhis  is 
pears,  and 
ion.  The 
1  Into  one 

Tliey  are 
su])i)ly  in 
)artly  the 
lical  vesi- 
j  increase, 
art  of  the 
•  placental 
,  first  two 
veins  dis- 

from  the 

phicental 
leparation 
re  abrupt 
"or  by  the 

ireviously 
\y  of  the 
ion  of  the 
ick  wards, 
nt  of  the 
rches  are 
er  of  five. 

as  some 
t  through 

In  man 
pear  and 
tids  (5  ), 


) 


DE  VELOPMENT  OF  THE  VASCUI.A  A'  S  VSTKAf.      300 

subclavian  (4  ),  arch  of  the  aorta,  pulmonary  artery,  ductus 
arteriosus,  and  descending  aorta  (Fig.  148).  The  veinn  that 
first  ajjpear  are,  as  alniady  stated,  the  omphalo-niesenteric 
which  soon  unite  to  form  one.  Next  is  formed  the  two 
umbilical  veins,  which  return  the  blood  from  the  ])lacenta, 
the  left  enlarging,  while  the  right  disaj>pears.  When  the 
liver  begins  to  be  formed  branches  pass  into  that  organ* 
and  give  origin  to  the  hepatic  vein.s.  This  organ  receives 
blood  from  two  sources,  the  portal,  and  the  und)ilical  veins. 
The  systemic  veins  are  formed  froa  pmr  trunk  veins,  two 
above,  and  two  below,  which  unite  into  a  canal  (sinus  of 

Fi;.'.  US.  V\]i  141». 


Aiirtic  arcliesiflvopuirsurosliowTi, 
thcui)|)erone!iilisai)pe(ir,  the  throe 
lower  remain,  and  reiiresent  tlio 
carotids  (.'■>),  the  sulxilaviaii  (4)iiiid 
arch  of  tlie  aorta  (3).  1,  Triinlis 
which  spriiii,'  from  the  ventricles  ; 
2,  descending  aorta,  the  left  (2)  is 
finally  obliterated;  the  ductus 
arteriosus  is  seen  at  the  junction 
of  the  arch  with  the  deaceiidin^f 
portion  (0). 


I)ia;;rum  of  the  develop- 
ment of  the  veins :  c,  c, 
cardinal  veins  ;  j,  j,  j'lK"- 
lar  veins  ;  h,  hc|iatic  veins; 
dc,  ducts  of  Ouvier  ;  sv, 
sinus  venosus. 


Cuvier)  on  each  side,  and  open  into  the  rudimentary  auricle. 
(Fig.  149).  The  two  above  are  called  the  anterior  cardinal, 
or  jugular  veins,  and  the  two  below  are  called  the 
posterior  or  inferior  cardinal  veins.  When  the  umbilical 
vein  is  formed,  it  at  first  communicates  with  the  sinus  of 
Cuvier,  but  after  the  inferior  vena  cava  is  developed,  it 
empties  info  the  latter.  The  auricle  now  receives  blood 
from  the  inferior  vena  cava,  and  the  sinuses  of  Cuvier 
which  now  become  the  right  and  left  supei;ior  vena  cava 
respectively.     The  left  vena  cava  finally  disappears  and  its 


,..,  f 


400 


REPRODUCTION. 


In 
I 

I 


JO, 


orifice  is  converted  into  the  coronary  sinus  ;  the  right,  forms 
the  superior  vena  cava.  An  anastomosing  branch  between 
the  anterior  jugular  veins  becomes  the  left  innominate,  and 
the  termination  of  the  right  jugular  the  right  innominate 
vein.  The  inferior  cardinal  veins  return  the  blood  from  the 
Wolffian  bodies,  vertebral  column,  and  parietes  of  the  trunk. 
The  inferior  vena  cava  is  formed  about  the  fifth  week,  and 
finally  receives  the  blood  from  the  inferior  cardinal,  and  the 
crural  veins.  The  upper  part  of  the  cardinal  veins  remains, 
the  riglit  c^e  as  the  vena  azygos  major,  and  the  left  as  the 
vena  azygos  minor  and  superior  intercostal.  The  middle 
portion  disappears,  and  the  lower  becomes  the  hypogastric. 

Devflopment  of  the  Alimentary  Canal  and  Glands. 
— The  alimentary  canal  is  formed  at  a  very  early  stage.  It 
is  at  first  closed  at  each  end,  by  the  blastodermic  layers, 
and  communicates  with  the  umbilical  vesicle.  It  consists 
of  three  parts  ;  the  anterior,  which  forms  the  pharynx  and 
oesophagus  ;  the  middle  which  forms  the  stomach,  intestines, 
and  upper  third  of  the  rectum  ;  and  the  posterior  which 
forms  the  middle  third  of  tlie  rectum.  The  lower  end  of  the 
rectutn  and  buccal  cavity  are  formed  by  a  depression  in  the 
middle  and  external  layers  of  the  blastoderm,  and  do  not 
communicate  with  the  common  cavity  till  a  later  date, 
hence  the  occasional  occurrence  of  imperforate  anus  and  im- 
perforate a3sophagus.  The  middle  portion  of  the  intestine, 
is  at  first  a  wide  groove,  which  becomes  converted  into  a 
straight  tube,  and  is  gradually  separated  from  the  umbilical 
vesicle.  It  now  becomes  divided  into  the  different  parts,  as 
the  stomach,  small  intestine,  and  large  intestine,  and  is  sus- 
pended in  the  abdomen  by  the  mesentery  which  attaches  it 
to  the  spine. 

The  principal  glais Js  are  the  limr,  pancreas,  spleen  and 
salivary  gla'tids.  The  liver  is  developed  from  two  promi- 
nences of  the  blastoderm  in  the  form  of  hollow  cones,  which 
involve  the  omphalo- mesenteric  vein,  from  which  they  re- 


DEVELOPMENT  OF  RESPIRATORY  ORGANS.     401 


■ight,  forms 
ch  between 
ninate,  and 
innominate 
od  from  the 
f  the  trunk. 

week,  and 
lal,  and  the 
ns  remains, 

left  as  the 
Che  middle 
lypogastric. 

ID  Glands. 
f  stage.  It 
rnic  layers, 
It  consists 
larynx  and 
,  intestines, 
irior  which 
r  end  of  the 
3sion  in  the 
and  do  not 
later  date, 
iius  and  ini- 
le  intestine, 
rted  into  a 
le  umbilical 
snt  parts,  as 
and  is  sus- 
attaches  it 

spleen  and 
two  promi- 
ones,  which 
sh  they  re- 


ceive branches.  These  prominences  are  developed  into  the 
right  and  left  lobes.  This  organ  is  of  large  size  in  propor- 
tion CO  the  body,  and  secretes  a  substance  which  is  poured 
into  the  intestine,  termed  the  meconium.  The  gall  bladder 
is  developed  as  a  pouch  from  the  hepat'o  duct.  The  salivary 
glands  are  developed  from  the  epiblast  lining  the  luuath,  in 
the  form  of  simple  canals  with  bud-like  processes,  sur- 
rounded with  protoplasm  and  communicating  with  the 
mouth.  The  canal  becomes  more  ramified  as  development 
proceeds.  The  pancreas  is  developed  from  the  hypoblast 
lining  the  intestine,  in  a  similar  way,  and  the  spleen  is 
developed  from  the  mesoblast,  proceeding  from  a  segment 
of  the  peritoneum. 

Development  of  the  Respiratory  Organs. — The 
lungs  first  appear  as  small  tubercles  in  front  of  the  oesoph- 
agus. They  are  formed  from  the  hyyoblast  of  the  alluieu- 
tary  canal.  They  at  first  open  into  the  (esoj)hagus,  buE, 
soon   a   separate  tube  is  formed   at  Fig.  150. 

their  point  of  junction  ;  this  is  the 
trachea.  The  primary  tubercles  thus 
formed  next  send  off  secondary 
branches  into  the  surrounding  meso- 
blast, and   these  again  tertiary  ones     a,  u.aeveioimieutof  thciung,*, 

1  .    ,      ,1  .  n  n  if,    tertiary  bran'ihes     and     air 

on    which  the  air  cells  are  lonned.  cLiis. 
The  diaphragm  appears  early,  in  the  form  of  a  fine  mem- 
brane  separating   the    lungs   from    the    Wolfiian    bodies, 
stomach  and  liver.  ' 

Development  of  the  Urino-sexual  Organs. — These 
organs  are  formed  from  the  mesoblast.  The  Wolffian  body 
or  primitive  kidney  may  be  seen  as  early  as  the  third 
week.  It  has  a  glandular  structure,  in  many  respects 
*  similar  to  the  kidney,  is  provided  with  an  excretory 
duct,  and  secretes  a  fluid  containing  urea  which  is  con- 
veyed to  the  bladder  It  pUaiiie  its  highest  development, 
about  the  sixth  week  ;  it  then  diminishes,  to  be  replaced  by 


i 


402 


REPRODUCTION. 


c 
t 

[ 

•ft 


I 


n*' 


i; 


the  kidney,  il)y  ppdad  sanears  the  end  of  the  third  month 
The  duct  of  the  WolfHan  body  is  formed  in  the  mesoblast 
behind    the    pleuro-j  ericoDeal    cavity.     The  duct  is    first 

hollowed  out,  and  then  the  tubes 
of  the  Wolffian  body  begin  to 
form  as  branches  of  the  duct 
which  terminate  in  Malpighian 
bodies.  Next  a  thickening  occurs 
between  the  Wolffian  body  and  the 
mesentery,  termed  the  Wolffian 
ridge  or  "geim  epithelium"  from 
which  the  testis  or  the  ovary  is 
developed,  as  the  case  may  be.  A 
groove  is  now  formed  internal  to 
the  Wolffian  duct,  called  the  duct 
of  Muller.  These  ducts,  together 
with  the  ureter,  when  formed, 
open  into  the  urogenital  sinus,  or 
termination  of  the  intestinal 
cavity.  The  Wolffian  ducts  re- 
main in  the  male,  and  form  the 
A,  ki.iney ;  h,  ureter ;  c.  Bladder ;  cpididymus,     vas     deferens     and 

u.   urachus  ;    k,  constriction   which    pipp„l{,fnrv      f\nok      nn      Pflph     cjidp 

becomes  the    urethra;    v.   Wolffian    ejaCUiaiOiy      UUCL      OH      eacil     'slue. 

body ;    o.    Wolffian    duct,    with    its 

opeiiinjf  below,  o';  n,  duct  of  Mitller, 

united  below,    from   the   two  sides. 

into  a  single  tube,  j',  whiih  iircsmts 

a    single    oi)ening.    .i,    between   the 

openings  of  tlie  Wolffian  <Uicts  ;  li, 

ovary  or  testicle  ;  i,,  gul  ernatuluni  .  n    .1        -ixr    mh  1       i.        i   •    1 

testis    or    round     ligan  ent    of   the    maiUS  01    the    Wolman  OUCt  WhlCh 

uterus;  m,  genito-urinarv  sinus  ;  s,      ,  i      1       .i  •  c  ,1 

o,  external  genitalia.  dcsccnds  to  the  vagina  lorms  the 

"  duct  of  Gsertnei."  The  ureter  is  formed  in  the  mesoblast 
in  which  the  kidney  commences  to  develope,  and  leads 
down  to  the  urachus.  The  kidney  is  developed  from  a 
series  of  c]ub-sha|>ed  mases,  in  which  are  formed  the 
calicos.  It  has  therefore  a  lobulated  appearance  which 
continues  for  some  time.  The  supra-renal  capsules  are 
developed  from  the  same  mass  as  the  kidney,  [and 
are  at  first  much  larger. 


A  small  portion  of  the  Wolffian 
body  lemains  in  the  female  term- 
ed the  parovariuvi,  while  the  re- 


DEVELOPMENT  OF  UTERUS  AND  VAGINA. 


403 


ird  month 
mesoblast 
ct  is   first 
the  tubes 
begin   to 
the    duct 
^alpighian 
ling  occurs 
idy  and  the 
!    Wolffian 
lum"  from 
e  ovary  is 
nay  be.    A 
internal  to 
d  the  duct 
s,  together 
m  formed, 
al  sinus,  or 
intestinal 
ducts    re- 
form the 
jrens     and 
each    side. 
Wolffian 
male  term- 
lile  the  re- 
uct  which 
forms  the 
mesoblast 
and  leads 
ed  from  a 
)rmed   the 
ice   which 
jsules   are 
Iney,  [and 


The  bladder  is  next  developed  from  the  urachus ;  this  is 
a  hollow  tube  wliich  connects  the  posterior  part  of  the  intes- 
tines with   the  allantois.      As  the  abdomen  closes  at  the 
umbilicus,  the  part  of  the  urachus  outside  the  body  forms 
part  of  the  cord,  while  the  portion  included  in  the  abdomen 
becomes  dilated  and  fusiform  at  the  lower  part,  and  forms 
the    bladder  ;    the    upper    part    becomes    obliterated   and 
forms  a  fibrous  cord  which  extends  from  the  summit  of  the 
bladder  to  the  umbilicus.      Sometimes,  though  very  rarely, 
this  part  remains  pervious  and  permits  of  the  escape  of 
urine  at  the  umbilicus.     The  testes  or  ovaries  which  are 
formed  on  the  inner  side  of  the  Wolffian  bodies,  soon  begin 
to  descend,  the  former  to  the  scrotum  and  the  latter  to  the 
pelvis.     This  was  formerly  supposed  to  be  caused  by  the 
action  of  a  muscular  organ,  the  gubernaculum  testis,  but 
this  is  not  now  g.  nerally  supposed  to  be  the  case.     The 
means  by  which  it  is  effected  are  not  known.     The  testicle 
in  its  descent  pushes  before  it  a  pouch  of  peritoneum,  be- 
hind which  it  lies,  which  ultimately  forms  the  tunica  vagi- 
nalis or  serous  covering  of  the  testicle. 

The  uterus.  Fallopian  tubes,  and  vagina  are  developed 
from  the  ducts  of  Mliller,  already  described.  The  union  of 
the  two  ducts  below  form  the  vagina,  cervix,  and  lower 
portion  of  the  uterus,  while  the  upper  portions  form  the 
upper  part  of  the  uterus  and  Fallopian  tubes.  This  explains 
the  occurrence  of  an  occasional  bicornute  condition  of  the 
uterus.  The  external  organs  of  generation  are,  at  an  early 
stage,  the  same  in  both  sexes.  The  urino-genital  opening, 
or  sinus,  is  formed  at  the  same  time  as  the  anal  cavity,  by 
a  reflection  of  the  epi blast  inwards.  There  is  first  seen  a 
tubercle  in  front  of  the  sinus,  the  genital  tubercle,  which 
is  soon  surrounded  by  two  folds  of  integument,  the  genital 
folds.  The  tubercle  is  surmounted  by  a  glans,  and  is  grooved 
upon  the  under  surface  (Fig.  151),  yet  no  distinction  of  sex 
can  be  made  out.  As  development  proceeds,  the  urino- 
genital  sinus  in  the  female  remains  and  communicates  with 

2.i 


404. 


REPRODUCTION. 


the  vagina;  the  genital  tubercle  retractn  and  forms  the 
clitoris,  and  the  foldings  of  integument  are  converted  into 
the  nymphae  and  labia  majora.  In  the  male,  the  genital 
tubercle  elongates,  the  glans  is  developed,  and  the  margins 
of  the  sinus  meet  on  the  under  surface  to  enclose  the  ure- 
thra. The  large  cutaneous  folds  form  the  scrotum,  which 
receives  the  testicles  about  the  eighth  month.  When  the 
urethra  fails  to  close,  hyposfoLclias  results,  and  an  appear- 
ance of  hermaphroditism  is  present,  which  is  increased  by 
the  retention  of  the  testicles  in  the  abdomen. 


I 

f 

?*■■■ 


forms  the 
'^erted  into 
he  genital 
le  margins 
3  the  ure- 
um,  which 
When  the 
m  appear- 
jreased  by 


APPENDIX. 


METRIC  SYSTEM  OF   WEIGHTS  AND    MEASURES. 

Equivalents. 


Metre 

Decimetre -zqi 

Centimetre '."*.'.".'.,.*.""     ^q 

Millimetre  (mm) '.'.*.'.'..'."!.*...'...' 

Micromillimetre  (mmm) 


or  391 
or  2i 
or       I 

039         or      tjV 
000039  or  ^^j-jj3 


inches. 


Gramme  ,- 

Decigramme *  '"'   j  ^^ 

Centigramme 1^4 

Milligramme  ...,......"      ore 


or  15^ 
or     i^ 

or      i 
or      ^ 


II 
II 
11 
II 


grams. 


II 
II 
II 


THE    METRIC    SYSTEM    IN    MEDICINE. 
Old  Style. 

MioT  gr.i  equals  

/si  or  ,5i  , ........"."   4 

/si  or  |i  „      '"^2 

The  decimal  line  instead  of  points  makes  errors  impossible. 
A  teaspoon  contains  4  gins.  ;  a  tablespoon  20  gms. 


Jletric. 

06  gms. 

ti 


AVERAGE    SIZES   OF   VARIOUS    HISTOLOGICAL    ELEMENTS. 
Fractions  of  an  inch. 


Air  Cells  ^o  to  ^i,. 


_ ,         -      "         10    -"    3  0  0     7 

Blood  Corpuscles,  Red,  ^^..^  


Metric. 

to 


••  n  White  3j)'oo  

Canaliculi  of  Bone  TTri^Tnr 

Capillaries,  7^-Vir 

Cartilage  Cells,  ^i^  to  ^^,^ „  to 

Chyle   Corpuscles,  -j^Vo 

^^^^^  Tl^oo  iO  J-^Tf     6    to 

Cones  of  Retina,  T^ion    

End-bulbs  of  Krause,  ^^ 


.12  mm 

71 

mmm 

8 

mmm 

1.4 

mmm 

8 

mmm 

12 

mmm 

8 

mmm 

mmm 

2 

mmm 

41 

mmm 

c 
c 

i 

h 

K 

M 

I 

ti 

K 

m 

\ 


By. 


406  APIENDIX, 

Epithelium,  Columnar,  j^,,^  to  .  ,, lo    to  7.1  mmm 

II  Squamous  si, i  to  .x^'ao    50     to  ic     mmm 

Fat  Cells,  j^o  to  „},<,  83     toji      mmm 

Granules,  y^l^-^  to  _.  J ^u 2.5  to    i     mmm 

Haversian  Canals,  .^,',0  to  j^'o,,    120    to  12     mmm 

Lacunae  (bone),  xfl'oo  ^4     mmm 

Lirabus  Luteus,  ^^  i     mm 

Malpighian  Bodies,  (kidney),  yA„  .2  mm 

II  II         (spleen),   ^^ .4  mm 

Muscle,  Striated,  ^^^  to  ^J^ 125     to  50     mmm 

•t       Nonstriated,  ^^7  to  j^^75^ 8.510    5.5  mmm 

Nerve  Cells,  5^-,,- to  y^Vt ^3     ^°  2,5  mmm 

II      Fibres,  (medullated)  ^^j^tj  to  Y2-J-„-vr  ....  12     to  2     mmm 

II  II       (non-medullated)  ^^j^  to  -B-^fVir--    6     to  4     mmm 

Ovum,  Ta( .2mm 

Pacinian  Bodies,  ^'o  to  iV  2.5  to  1.7  mmm 

Papillae  of  Skin,  3^^  to  ^7^ 25to     .1  mm 

II      of  Tongue,  tV  to  Vo  2       to     .3mmm 

Tactile  Corpuscles,  ^io  .imm 

Tubuli  Uriniferi,  sin 50.    mmm 

Villi,  Vo  to  ijio  5  to     .imm 


AVERAGE    SPECIFIC   GRAVITY   OF    VARIOUS    FLUIDS. 

(Water  =  1000). 


Bile 1020 

Blood 1055 

Cerebro-Spinal  Fluid 1006 

Chyle 1024 

G^tric  Juice 1005 

Intestinal  Juice loii 

Lymph 1020 

Lungs   when   fully  distended  with  air,  126;  when  deprived  of 
air,  1056  ;  ordinary  postmortem  condition,  345  to  746. 


Milk 1025 

Pancreatic  Juice 1012 

Saliva  1005 

Serum  1026 

Sweat  J004 

Urine  1020 


AVERAGE   QUANTITY  OF    VARIOUS    FLUIDS    SECRETED 
IN    TWKNTY-FOUR    HOURS. 
Ota.  <pns.      I  07.8.  gnis. 

Bile 35  =  1100  I  Saliva 30  =    930 

Gastric  Juice 240  =  7500  j  Sweat 25  =     780 

Pancreatic  Juice.     14  =    440  [   Urine  40  =  1250 


'  7-1 
re 

3' 
>    I 

12 

I 
.2 

•4 
5° 
S-5 

3    2.5 
D    2 

3    4 
.2 

3    1.7 

0       .1 

3     -3 
.1 

50- 

)     .1 


IDS. 


mmm 

mmm 

mmm 

mmm 

mmm 

mmm 

mm 

mm 

mm 

mmm 

mmm 

mmm 

mmm 

mmm 

mm 

mmm 

mm 

mmm 

mm 

mmm 

mm 


1025 
1012 
1005 
1026 
J  004 
1020 


deprived  of 


LE'J'ED 


30 

25 
40 


gnis'. 

930 
780 

1250 


APPENDIX. 


REACTION   OF   THE   VARIOUS    FLUIDS. 


407 


All  the  fluids  of  the  body  have  an  alkaline  reaction,   except 
the  following,  which  are  acid  : 


Gastric  Juice. 
Sweat. 


Urine. 

Mucus  of  the  Vagina. 


CLASSIFICATION  OF  THE  ANIMAL  KINGDOM. 

(  Gegenhauer.) 


INVERTEBRATA. 

i  Rhizopoda  ;  amoebae,  foraminifera. 

-:  Gregarinre. 

I  Infusoria  ;  vorticella,  paramaecium. 

f  Spongine  ;  sponges. 

\  Acalephae ;     hydra,     coral,     sea-anemone, 
polyps,    medusiB,  beroe. 

f  leeches,  earth   worm,   round  worm,   thread 
\  worm,  tape  worm,  guinea  worm,  bryozoa. 

star-fish,  sea-urchins,  sea-cucumber. 

/  Branchiata  ;  crab,  lobster,  barnacle. 

(  Tracheata;  scorpion,  spider,  beetle,  cock- 
roach, bee,  ant,  butterfly. 

f  Ecardines ;  lingula. 

(  Tcsticardines ;  terebratula. 

I  Placophora  ;  chiton,  cryptochiton. 

I  Conchifera  ;  oyster,  cockle,  whelk,  snail,clio, 
argonaut,  cuttlefish,  nautilus. 

J  Copelata ;  oikopleura. 
\  Acopa ;  salpa,  pyrosoma. 

'     VERTEBRATA. 

Acrania  :       Leptocardii ;  amphioxus. 

r       •  f       i  Cyclostomata  ;  myxinoidea,  petromyzontes. 
l^ramota :  |  Onathostomata. 

i  Pisces. 
(a)  Anamnia  :     \  Amphibia  ;  frog,  newt,  triton,  sal- 
(  amander. 

/'Reptilia  ;  lizard,  snake,  crocodile. 
)  chameleon,  tortoise. 

Aves. 


Protozoa : 
Coelenterata  : 

Vermes  : 
Echinoderma 
Arthropoda : 

Brachiopoda : 
Mollusca : 

Tunicata  : 


(b)  Amniota : 


\ 


Mammalia. 


ADDENDUM. 


r 

Mr' 


Spuuiiiieit  of  blood  showing:  marked  leucocytha3)iiia.    Tlie  proportion  of  wliite  to  rod 
cwrpiuelex  is  as  one  to  seven. 


if  wliite  to  rod 


INDEX. 


Abdiicena 

Absorption 

Mechanism  of 

by  villi  and  lactoals 

by  blood  ves.sols 

by  lymphatics 

Acini  of  Ijiver 

Adipocero 

Adipose  tissue 

Appearance  and  properties  of 

Function  of 

.lEsthesionietcr 

Air,  chany:es  in  respired 

(Quantity   respired 

Breatbin<f  or  tidal 

Coinpleniental 

Suitplcineiital 

Residual 

Mininuun  quantity  in  schools 

Air  Cells 

Albinoes 44, 

Albumen 

Composition  of 

Function  of :}7, 

Tests  for 

Albuminose 37, 

(•rijjin  and  functio;:  of 

Albuminoid  substances 

Alcohol 

Amnion  and  allantois 

Ain(Bba 

Ampidla) '207, 

Anelectrotonus 

Ajihasia 

Aponeuroses 

Apophysis 

Aqueous  humor 

Area  pcllucida 

Areolar  tissue 

Function  of 

Arrectores  pilorum 

Arteries,  Structure  of 

Function  of  elastic  tissue 

Muscular  tissue  of 

Vasa  Niisorum  of 

Anastomosis  of 

I'ulse  of 

Inlluenee  of  nerves  on 

Velocity  of  circulation 

Articulation 

Aspliyxia 

Associate  function  of  Nerves 3:5(j, 

Astijjfmatism 

Auditory  Nerves 

Auditory  vesicle 

Automatic  action 

Axis-cylinder 


PAGE. 

..  331 

..   158 

..  163 

..   165 

..   160 

..  107 

..  253 

..     30 

..     65 

. .     65 

..     06 

..   308 

..   -231) 

..   235 

..   235 

..  235 

..  235 

..  230 

..  230 

..   232 

115 

35 

30 

l!)0 

37 

142 

38 

33 

129 

380 

54 

360 

250 

319 

00 

70 

34!  I 

oS3 

(>4 

04 

115 

213 

214 

215 

214 

210 

217 

210 

225 

374 

243 

342 

!457 

330 

395 

277 

281 


B 

Bacterium 35 

Basement  membranes 58 


Paoi. 

Basement  membranes.  Function  of . . . .     59 
Bernard  on  the  function  of  the  liver. . .  150 

Bile 147 

Appearance  anil  properties  of 148 

Chemical  composition  of 148 

Bile  salts  or  bilin 149 

Function  of 151 

Tests  for 153 

Bilirubine 44,  149 

Blliverdine 46.  140 

IJhistodennic  niem)>rane 382 

Uleedin]^'',  effects  of,  on  blood 183 

Blood,  Elements  of I(i8 

Quantity  of 168 

Physical  character  of 108 

Jlicroscopical  a|)i)car.ince  of 169 

lied  corpuscles  of 170 

White  corpuscles  of 173 

Oriyin  of  Corpu-ides  of 174 

Development  i)f  Corpuscles  of 175 

Chemical  composition  of . . .    177 

Ilenioyloliine 178 

Distinction    between    human    and 

animal  blood 100 

Difference   between    arterial    and 

venous 180 

Portal,  renal,  and  hepatic  venous 

blood 180 

Oases  of 181 

Causes  of  Color  of 182 

Influence  of  venesection  on 183 

"  Starv.atiiiu  on 184 

"  Iron  and  flesli  diet..  ..   184 

"  Ajje  and  se.x 185 

"  Disease  on 185 

Blood  Poisons 188 

Coagulaticin  and  vital  |)roperties  of.  188 

Time  required  ior  coajfulation 189 

Theories  of  coajfulation 190 

Cupped  and  P. iffed  condition  of. ..   191 

Coa!,'ulat'on  ot  promoted 192 

retarded 191 

Function  of  fibrin  of 194 

"  red  corpuscles  of 195 

"  white  corpuscles  of. . .   196 

"  albumen  of 190 

"  fats  of i97 

salts  of 197 

Relation  of,  to  livin;,' organism. . ..  198 

Globuline  of 178 

Increase  of  fibrin  of 185 

Circulation  of  blood 200 

Changes  of  in  respiration 242 

Bone 72 

Appearance  and  properties  of 72 

Chemical  constituents  of 72 

Structure  of 73 

Haversian  canals  of 73 

Lacuna;  and  canaliculi  of 75 

Articular  lamella  of 75 

Development  of . , 75 


III 


410 


INDEX. 


c 

to 

i 

h 

I 

"-. 

m 

8 

I 


Haur. 

Bono,  (Irowth  of 78 

Briiiii 310 

Avuragc  weijfht  of 310 

Htructuro  of 311 

Vasculiir  Huppiv  of 310 

VentrirluH  of 31(1 

Function  ol,  Ac :tl7 

Uuntru  for  laiiKuaij;e 310 

"          vision 315 

"         heurint; 315 

Bronchoiiule  or  noitro 275 

Bro\vn-8d(|uar(i  on  Hpinal  uord 3U1 

Brunnur's  i^lanilH Ill 

BurHU! 102 

Butter  acids 208 


C 

Caiiuliuuti 

Canal  o(  I'etit 

Capillurio.M,  Structure  of 

Circulation  in 

Influence  of  nerves  upon 

Velocity  of  Circulation  in 

Carbonic  acid,  Inhalation  of 

How  affected 

Ih)W  favored 

Cardinal  veins 

Cardioff  rapli 

Cartilnjfe 

Appearance  and  jiroperties  of 

Tenijiorary  and  I'ernianeut 

Hyaline 

Reticiilur 

Fibro-cartilajfc 

Vascular  snpjtly  of 

Cartilagine  or  Chondrinc 

Casein 40, 

Oriifin  and  function  of 

Cauda  Kquina 

Cause  of  Orjfanization  .  . . :   :  . . 

Cells 

Ueflnition  of  a  Cell 

Variation  in  shape  and  size 

•Structure 

Cell  nuclei 

Cell  contents 

Color 

Development  and  j,'rowth ol, 

Permanent  ctiantfc  of  shape 

Tcniixirary  chanH;e  of  sliape 

Function  of  Cells   

JIaiiifostation  of  cell  life     

Cells  of  Purkinje 

Cement  substance 03, 

Cerebellum 

Structure  of 

Peduncles  of  (crura) 

Cerebral  vesicles 

Cercbrine 

Cerebro-spinal  nerves 27(1, 

Cerebrum 

Averajfe  wci(fht  of 

Structure  of 

Convolntiiins  of 

Sulci  of 

Lobes  of 

Fissures  of 

Areas  of  (Fcrrier) 

Ventricles  of 

Vascular  supply  of 

Function  of . . ." 

I  'rura  cerebri 


HM 

222 

223 

224 

225 

231) 

240 

242 

300 

200 

t)7 

07 

07 

(18 

CO 

70 

70 

42 

208 

41 

200 

55 

47 

47 

47 

48 

40 

50 

50 

ri3 

53 

54 

50 

57 

308 

113 

307 

307 

30S 

393 

4(i 

285 

310 

310 

311 

311 

312 

312 

313 

314 

310 

310 

317 

323 


I'AOB. 

Cerebration,  unconsclouil    323 

Cerundnous  Rlands 121 

Cervical  fissures 804 

Cerumen  of  ear H58 

Chalaza 370,  381 

Chalazifcrous  membrane 381 

(Jholesterinc 33,  140 

Chorda  Dorsalisor  Notoehord 384 

Chorion,  formation  of 388 

Choroid 344 

Chromatic  aberration SIfi 

Chyle,  Molecular  base  of 101 

Comiwsition  of 102 

ChvliHcation 144 

Chymillcation 1!J0 

Ci>'atricula 384 

Ciliarv    Ligament 340 

Ciliary  Muscle 346 

Ciliarv  Processes 345 

Cilia 00 

(irowth  and  motion  of 54,     00 

Ciliated  e)iithelium 100 

Circulation 200 

Course  of,  in  the  adult 202 

Proofs  of 203 

Peculiarities  of . .    .    226 

Velocity  of 225 

Vitelline  circulation 307 

Fcetal 227 

Cleft  i)alatc 304 

(Joaffulable  Ivmidj 58,  106 

Cochlea         .". 360 

Coflfee 130 

Collagen 43 

Coloring  matters 43 

Colloids  and  Crystalloids 104 

Colostrum 208 

Coldblooded  animals 244 

Connnunication  of  lu'rvous  impressions  204 
Conduction  of  nervous  impressions —  204 

Conjugation 376 

Connective  tissue 00 

Corium  or  oitis  vera llf> 

Cor>  ea,  structure  of 343 

Con)ora  am vlacea '-4,  284 

Corpora  striata 324 

Corpora  quadrigemina 323 

Corpus  lutcum 380 

Corpus  calliisuni 324 

Corptisclcs  of  the  Blood 170 

Origin  of 174 

Develojinicnt  of 175 

Coughing 238 

Craiuo-spinal  axis 279 

Cranial  nerves 329 

Creatine  and  creatinine -204 

t!retinism 275 

(.'rying 238 

Crystalline  lens  and  capt    '" 349 

Cumulus 379 

Cyanosis 229 

Cytoblastcnia 50 

Cytogencsis 51 

Laws  of 51 

Modes  of 52 

Conditions  necessary  to 53 

D 

Daltonism 357 

Decidna  Vera 389 

Reflexa 300 

Serotina 390 


INDKX. 


411 


I'AOB. 

328 

121 

81)4 

8f)8 

...371»,  381 

381 

33,  140 

384 

388 

344 

aifi 

1(11 

102 

144 

130 

384 

346 

346 

345 

00 

....54,     119 

100 

200 

202 

203 

22« 

225 

397 

227 

394 

...  68,  196 
360 

mo 

43 

43 

104 

268 

244 

prcssidiis  204 
s»ioiiM. . . .  294 

376 

00 

115 

343 

24,  284 

324 

323 

380 

324 

170 

174 

175 

238 

270 

320 

204 

275 

238 

349 

379 

229 

50 

51 

51 

52 

53 

357 

.S80 

.390 

300 


I'AQII. 


Deou8)iatioii  of  Medulla 

Dcfocatiun 

Dcgliitltioti,  MuclmniHin  of 

Deiitinu 

l)uvelo|iiiioiit  of 

Devclopinont  of  collo 

of  tho  embryo 

"     Hpiiiu,  craiiiiiin  and  nervous 

Hystoin 

"      fuce 

"     eye,  uiir,  noso 

"     extruniitius 

"     vaacular  Nystem 

"     intestinal  cnnul  und  glands. . 

"     lunifs 

iirino-sexual  organs 

nerve  centr  > 


Diabetic 
Digestion 

Kate  of 

Influciiuo  of  nerves  on ... . 

Artificial 

Movements  of  stomach  in. 

Digestive  fluid 

Discus  Proliiferus 

Dorsal  |)lates 

Dreams 

Drink •   

Ductless  glands 

Diapliysis 


E 
Ear,  Structure  of 

IJones  of 

Ectopia  Vesicas 

Elastic  tissue . .   * 

Elasticine : 

Electricity ; 

Currents  of .* 

Phenomena  of.  in  man 

"  "    animals 

Electrotonus 

Elementary  forms  of  tissue 

Elen.ents  of  respiration 

Embryo,  development  of 

Embryonic  spot 

Emotions 

Enamel 

Develojnnent  of 

Encephalon 

End-bulbs  of  Krause 116, 

Endosmosis  and  exosmosis 

Epiblast 

Epidermis 

Epiglottis 

Epithelium 

Tessolated 

Columnar 

Ciliated 

Erectile  tissue 

Excito-motor  nerve  action 212,  219, 

Excretine 

Expiration 

Muscles  of. 


304 

160 

137 

79 

82 

51 

302 

303 
394 
395 
390 
397 
400 
401 
401 
300 
125 
143 
143 
14^ 
144 
144 
379 
383 
328 
128 
270 
76 

358 

359 

259 

62 

43 

248 

248 

249 

251 

250 

46 

120 

392 

383 

322 

80 

81 

303 


Eye. 


Structure  of 

Accommodation  to  vi.slon. 
Simultaneous  action  of . . . 

Essential  parts  of 

Blind  spot 


280 
103 
384 
113 
370 
96 
97 
98 
100 
227 
277 
157 
234 
234 
343 
843 
352 
365 
350 
355 


I'AUK. 

Facial  nervo,  Paralysis  oi    333 

Paeultlus,  Intellectual 320 

En.'ees,  Analysis  of 167 

Fats  and  oils 20 

PliVNlcal  appearance  of 30 

Function  of 82,  00 

Fenestra  ovalls  and  rotunda 300 

Formonts 34,  136 

Fil)rous  tissue 60 

Fibrocartilugo 70 

Fibrino..... 38 

Physical  a])pearance  of 30 

Coa^'uiatlon  of 39 

Function  of 40,  1114 

As  elTete  material 40,  1 95 

Filunj  termlnale 296 

Fission,    or    Fissiparous    multiplica- 
tion  62,  376 

Fine  adjuster  of  tho  eye 353 

FcL'tal  circulation 227 

Changes  in,  after  birth 220 

Follicles 108 

Food 126 

Cla-sslflcation  of 126 

Illatogenetic  substances  of 120 

(Quantity  of 127 

(Quality  of 128 

Force,  nervous 20.'V,  326 

Fovea  centralis 347 

Frontal  sinuses 341 


P 


Facial  nerve 332 

Division  of,  for  tic  doloureux 332 


Galvanic  pile 249 

Ganglion  Inipar 330 

Ganglion  of  Hibes 330 

Ganglia  of  the  Nervous  System 270 

of  the  Svmpathetic 337 

Structure  of 284 

Gases 22,  181 

Gastric  juice.. ..    140 

Physical  appearance  of 140 

Chemical  composition  of 140 

Function  of 142 

Gelatine 14,  43 

Gelatinous  tissue 71 

Gemniiparous  multiplication 52,  376 

(Jeuenitlon,  True 376 

Genital  tubercle  and  fold 403 

Germ  Cell 379 

Germinal  Vesicle 379 

Spot 279 

Membranes 59 

Matter 47 

Globullne 41,  178 

Glottis 370 

Gli>ss<)i)haryngoal  Nerve 333 

Glycogen 25 

Glycogenic  function  of  I/iver l.'iO 

(J(il)let  or  Hccher  culls 99 

Graiudcs  ( u-  .Molecules 57 

(iraafian  Vesicles 379 

Growth  of  Bone 78 

Nails 118 

Hair. 119 

H 

Hiomadynamometer 211 

Hair.  .."... 118 

follicle 120 

Hare-lip 394 

Haversian  system 74 

Canals 74 


412 


INDEX. 


c 
c 

^ 

n 
I 

S 

r 

I 

« 


Paur. 

Heart 200 

Htmeluronf 204 

VoMKols  uml  Norvos  of 206 

Actidii  of 206 

Soiiiuls  of 207 

Khythni  of  2(18 

Ciumus  of  soiukIm  of 208 

V/onlH  roprcsoiitiiiK  nouiuIh  of 208 

Iii\|)Uliie  of 2011 

Freciiiency  aiul  force  of  outluii 201) 

I'lfluence  of  nerves  on 211 

K\('ito-inotoruiiiliiiliil)itory  nerves  211 

Heariiitf ' 358 

Mei^haniMni  of M(J2 

Sense  of,  impaired 'Mii 

Heat 244 

Theory  of  |>ro(iuutioi>  of 245 

IiiHuuncu  of  nerves. ...    246 

Loss  of,  by  evaporation 247 

Latent 247 

Development  of,  in  muscle 1)1 

Hematine 178 

Hemofflolilne 43,  178 

Hepatic  cells 254 

Hiccup 231) 

Hippiiriu  acid 2(13 

Ilistojfeiietic  substances  of  food 120 

Klemcnts  of  blood 108 

Humor,  aipioous 340 

Vitreous 340 

Huntfor 130 

Ilypernictropia 350 

Hypoblast 384 

Hypoglossal  nerve 333 

Hypospadias 404 

I 

Ideas 321 

Ideo-niolor  action 270,  317 

Inanition 1,'il 

Ima^'e  formed  on  the  retina 351 

Imi>ulse  of  the  heart 200 

Impressions 280,  320 

Kegistration  of 281,  320 

Inhibitory  nerve  action. .  .212,  210,  301,  334 

In.salivation 134 

In8)>iration 234 

Muscles  of 234 

Instinct  and  intelligence 318 

Intellect ;>20 

Intellectual  faculties 320 

Integument 112 

Kiiithelium  of 113 

Color  of 114 

Coriumof 115 

Appendages  of ll(i 

Papilla;  of 110 

Function  of 122 

Intestine  (large) 155 

Intestinal  juice 145 

Appearance  and  i)roperties  of 145 

Function  of 145 

Intestine,  villi  of.. 110,  158 

Inter-cellular  passages  in  lungs 232 

Involution  of  the  uterus fA,  392 

Iris,  structure  of .  345 

Irradiation 364 

K 

Katelectrotonus 250 

Keratine 43 

Kidney 250 


I  PAok. 

I   Kidney,  Structure  of 260 

I          Malpighian  bodie§  of 2)i7 

Tubull  urinifcri 267 

Pyramids  of 268 

Papillie  of 257 

Vessels  and  nerveH  of 268 

Sinus  of 269 

Function  of 260 

Kymograph 211 


Labyrinth 360 

Vestibular  portion  of 361 

Lacteals : 168 

Absorption  l)y 105 

Lactose,  or  sugar' of  milk 20,  208 

Lacunio  of  bone 76 

Larynx,  organ  of  voice 370 

Structure  of 370 

Vocal  cords  of 371 

Ventricles  of 370 

Muscles  of 374 

Laughing 238 

Laws  of  cytogenesis 51 

of  Nerve  action 201 

regulating  transmission  of  light...  351 

of  nervous  distribution 303 

Lccithine 45 

Lenticular  glands 140,  155 

Lenses 350 

Leucine 46 

Levers 92 

LicberkUhn's  follicles 109 

Light , 248 

Ligaments 60 

Limbcus  luteus 347 

Lime  phosphate . . .  .^. 19 

Carbonate 19 

Li(|uor  Amnii 387 

Liver 252 

Structure  of 253 

Hepatic  cells  of 254 

Function  oi 147 

Vessels  of 264 

Locomotion 04 

Lungs 230 

Structure  of 231 

Air  cells  of 232 

Vessels  and  nerves  of 233 

Action  of 233 

Exhalation  of  Carbonic  Acid  by .. .  239 

Inhalation  of  Oxygen  by 241 

Luteine 45 

Lyni|)h,  composition  of 160,  102 

Lymphatic  vessels 159 

Structure  of 160 

Absorption  by 167 

Lymphatic  glands 100 

M 

Magnesium  i)hosphate  and  eari)onate. .     22 

Malpigbian  bodies,  Kidney 256 

Bodies,  Spleen 271 

Pyramids 257 

Manmiary  CMands 266 

Structure  of 267 

Milk 267 

Chemical  composition  of  milk 267 

Colostrum  of 268 

Effect  of  medicinal  agents  on 269 

"       emotions  on 209 

Margarine 20 


INDEX. 


413 


Paoii. 

....  250 

....  'A7 

...  267 

....  2r)8 
.. ..  2r.7 

....  2fi8 

....  'iCM 

....  '2fiU 

....  211 

...  ;jriO 
....  :»6i 

....  l.'iS 
....  Ktf. 
.29,  2(W 
....  76 
....  :<70 
....  ;t70 
....  «71 
....  -MO 
....  374 
....  238 
....  .-il 
....  2i)l 
t...  361 
....  303 
....  45 
140,  165 
....  350 
....  40 
....  92 
....  100 
....  248 
....  «0 
....  347 
....  19 
....  19 
....  387 
....  262 
....  253 
....  254 
....  147 
....  264 
....  94 
....  230 
....  231 
....  232 
....  2.'« 
....  233 
V...  239 
'...  241 
....  45 
160,  102 
.  ..159 
....  KiO 
....  107 
....   100 

22 
256 
271 
257 
266 
267 
267 

fmilk 267 

268 

Its  on 269 

269 
29 


I'AOK. 


.MarHliuiI  Hall  on  Mpiiiikl  cord 

.MiiNtinttloii 

.MllHL'IU!*  of 

.MiitiTtiul  inviiibraiiuH 

.MikturiuliHt  doc'trino 

.Muconiuiii 152, 

.Mudiillu  oldonxuta 

.Structure  of 

Kuiicticin  of 

DuCUHHUtloM  of 

.Mcdullutud  nurvu  fibroM 

MulxHiior'M  pluxua 

.Vluliiuinu 

.Moiul)riiii()UH  uxpaiiMton!* 

Structure  of    

.McinbnineN  (Mhu|iU') 

.Meinbraiie-t  ul  the  fcutus 

.Meiul)ruiiii  <!riiuulosik  , , , 

Menibrurm  'r.\  iu|iaiii 

.Mesenteric  lilundH 168, 

McHinerisin 

Mcsoldiist 

Mesoce]>liiiloii 

.VIetanior|ilioHis  in  iininiulM 

Metajfenesia 

.Mind-force   

.Mind,  ami  Its  relation  to  tlio  body  .... 

Morbus  Cieruleus   '. 

Micrococci    

Micropyle 

'  .Mind,  Influonce  over  the  body 

.Morbus  Addisonii 

.Motion,  cause  of .14, 

Ciliary 54, 

Motorial  end-plates 88, 

.Motor  oculi 

.Mucous  McniliraneH 

Structure  of     

Appenda|,'es  of    

Mucus 

Chemical  ci  mstitucnts  of 

Mucine  or  .Mucosinc    42, 

Mulberry  .Mass   

Multiplication  by  subdivision .J2, 

b.\'  i^enunation   .">2, 

.Muscle  

Striated 

Primitive  fibres  of 

"  Kibrilhe  of    

Non-striated    

Mode  of  development   

Attachment  of,  to  tendons 

Chemical  composition  of 

Vascular  iind  nervous  supply 

Properties  of    

Sound  in  contraction  of 

Heat  in  contraction  of  

Elasticity  of 

Rigor  mortis  of 

Action  of 

.Muscular  sense. 301), 

.Musculine  or  myosine 

Muscularis  mucosie   

Myolemma  

.Myojua 

N 

Nails 117 

Nervous  system 276 

Of  lower  animals    '277 

Cranio-spinal  axis  of 279 

D.ajiriuu  i>f  action  of 279 


802 
132 
138 

58 

324 

268 

30.S 

803 

806 

804 

281 

140 

44 

96 

9(1 

68 

391 

379 

868 

160 

328 

884 

80(1 

377 

377 

826 

324 

229 

35 

378 

327 

274 

89 

1«) 

288 

330 

103 

106 

105 

104 

104 

104 

382 

376 

376 

83 

83 

84 

84 

85 

8(1 

87 

87 

88 

89 

91 

91 

91 

91 

92 

368 

42 

139 

84 

350 


pAna. 

NurvouH  system.  Nerve  ■re 280,  21.0 

Htructure  of    2S1 

NervellbruH 281 

Nerve  colls 2«;< 

(ian^lia  of 284 

(Jliendital  uom|>uHltion  of 284 

IMstribution  of  nerve  Hbres  285 

Plexuses  of    285 

<  )ri){in  and  tonniiiatlon  of 286 

Function  of  nerve  llbn:s 280 

"         of  nerve  centrox 298 

AtTerent  and  efferent  nerves 289 

Kxcitability  ot  nerves 290 

Laws  of  action  of  nerves 291 

development  of  nerve  tissue 292 

Ite^fcncratioii  of 293 

Vascular  supplv  of    298 

ilcHex  action  of -MM),  296 

Automatic  action  of 277 

Koree  (vis  nervosa)    296 

Nervous  polarity    ,.  ...   296 

Nervi  nervorum 288 

Nerve  arc 280 

Centres,  function  of '03 

(Jonduetion 294 

Connnunicaiion 294 

Nourilennna 281 

Neurotflia 288 

Nitro>{cuous  substances 16 

"  erystalli/able 46 

Non-medullated  nerve  llbres 281 

Notes,  of  voice,  chest 373 

Falsetto    37.'l 

Nucleus    49 

Nucleolus .'>0 

O 

Odoriferous  glands    121 

Oils  and  fats    29 

Oleine    29 

Olfactory  nerves    329 

Optic  nerves    ">30 

Chiasma  of  288 

Optic  thalamus  324 

t»ptlc  vesicle    396 

Ora  scrrata 347 

Org.inic  substances    15 

Putrefaction  of  36 

O.sniosis 163 

( >steoblasts 77 

Ovaries .•J78 

Ovicapsule   379 

Oviducts,  action  of ."{80 

Ovum 379 

Development  of 382 

Sejrinentiitiou  of 3.S2 

Oxygen 22 

Amount  inhaled  by  lungs 241 

P 

Pacinian  corymseles 287 

Pancreatic  juice 145 

Appearance  and  proiierties  of 146 

Chemical  composition  of 14(1 

Function  of 146 

Panerc;itine    .. 42,  146 

Panniculus  adiposus (i5 

Papiliie ....106.  116 

Paralysis,  alternate .SO? 

(Jognate 307 

Parovarium 402 

Partiiritiou    3'./'2 


c 
c 

I 

L 

r 


414 


INDEX. 


I'athetio  iieivu 

Paveiiieiit  opitholiuin 

Pcpsiiie 41, 

Peptic  follicles 108, 

Peptone  ;!7, 

Perception   

I'ersinrution    

("lu'iuical  constituents  of 

Function  of ...  r. 

Payer's  glands    . . . .'. 

Pliarynffeal  arches 

Phrenoloffy,  absurdity  of 

Pit,'nient  cells " 

Placenta,  formation  of 

Plastic  elements  of  nutrition 12(5, 

Pneuuiojfastric  nerve   .   

Function  of 

Division  of    '2M7, 

Inhibitory  action  of 21'2, 

.Stinudation  of 212, 

Pons  Varolii 

Structure  and  function  of 

Poiassiuui  clilorido 

Prehension 

Presbyopia 

Pressure,  sense  of 

Primitive  trace 

Primitive  or  primordial  cells 

Primary  forms  of  tissue 

Primary  memhranes 

Protein  compounds 

Protoplasm 47, 

Protovertehriu 

Proximate  pniicii)les 

Definition  of 

Mode  of  extraction 

("lassitication  of 

First  class  of 

.Second  class  of 

Third  class  of 

Ptosis 

Pulse 

Head-wave  of 

Venous 

Pinictuni  saliens 

Putrefaction  ot  nitrojrenous  matters. .. 

Pvramids  of  Ferrein 

I'ytaline 42, 


I'AdB. 

..  «3] 

t)7 

142 

139 

142 

321 

122 

122 

123 

111 

394 

:{19 

114 

391) 

24.'i 

333 

:i33 

334 

3,34 

334 

3(Ht 

30(t 

18 

132 

350 

308 

383 

382 

40 

59 

34 

50 

385 

14 

14 

14 

15 

10 

22 

33 

330 

217 

217 

220 

307 

35 

2.58 

135 


K 

Ued  blood  corpuscles 170 

Function  of 195 

Size  of,  in  different  animals 171 

Color  of 172 

Reflex  action 295 

UeKisterinjr  (jan^'lia 281 

llcproduction 375 

Three  modes  of   375 

Action  of  male  in 377 

Action  of  female  in 378 

Respiration 230 

.Mechanism  of 233 

[''re<iuency  of 235 

(Quantity  of  air  respired 235 

Hreathinif  air 235 

Coniplcmental  air 235 

Reserve  air 235 

Residual   air 230 

Infhience  of  nerves  in ..  237 

Modiflcation  of  movements  of 238 

rhany:es  in  air  duriny 230 

Changes  in  the  blood  by 242 


Paok. 

Respiration,  Effects  of  the  arrest  of  ...  243 

Elements  of  (Liebi^') 120,  245 

Retina,  structure  of 347 

Impressions  on 351,  354 

Reticular  connective  tissue 71 

Retinacula 379 

Rij^or  mortis 01 

Rima  jjlottidis. . .    371 

Rods  of  Corti 301 

Rhythm  of  the  heart 208 

8 

Saccharose 28 

Salivary  glands,  structure  of 134 

Saliva 135 

Composition  of 135 

Function  of 130 

Saponification 29 

Sarcode 47 

Sarcous  elements 85 

Sarcolcmma 84 

Sclerotic 343 

Sebaceous  iflaiids 120 

Secondary  deposit 50 

•Secretinjr  ({lands 252 

Segmentation 331 

Semen  or  spermatic  fluid 320 

SeniicircuUr  canals 300 

Sensations 320 

Subjective  and  objective 321 

Serous  membranes 101 

Structure  of 103 

As  lvmi)h  sacs 101,  159 

Sight  ..'. 343 

Siiihing' 238 

Sinus  of  Cuvier 399 

Simple  fibres 57 

Membranes 58 

Sleep 327 

Smell 340 

Sneezing « 238 

Sobbing 239 

Sodium  chloride 17 

Function  of 18 

Sodium  and  potassium  carbonates 20 

Phospliates 20 

Sulphates 21 

Solitary  glands Ill,  107 

Somnambulism 328 

Sounds,  subjective 304 

Articulate 374 

Muscular 01 

Special  senses 340 

Siiectrum  of  bile 153 

Spectrum  of  hemoglobi'.ie 179 

Sperm  cell ''70 

Spermatozoa 377 

Spherical  aberration 353 

Sphygmogra))!! 218 

Spinal  accessory  nerve 335 

Function  of 335 

Spinal  cord 290 

Structure  of 297 

Spinal   nerves 298 

Function  of 299 

Reflex  fnnction  of 301 

(.h'ossed  action  of    300 

Hrovvn-Sc(|uard's  views  on 300 

Marshall  Hall's  vi  -ivs  on 302 

Constant  activity  of 302 

Spiritualist  doctrine 325 

Spirometer 230 


INDEX. 


415 


Paqe. 

rest  of  . . .  243 

1-20,  246 

347 

351,  364 

71 

379 

91 

371 

301 

208 

28 

134 

136 

135 

13(5 

29 

47 

85 

84 

343 

120 

50 

252 

331 

320 

3(!0 

320 

321 

101 

103 

101,  15!) 

343 

238 

399 

57 

58 

327 

340 

238 

239 

17 

18 

nates 20 

20 

21 

Ill,  l(i7 

328 

304 

374 

91 

340 

153 

179 

.•«76 

377 

353 

218 

335 

335 

290 

297 

298 

299 

301 

300 

11 300 

302 

302 

326 

236 


Paor. 

Spleen 270 

Structure  of 270 

Mal))i(;hiaii  bodies  of 271 

Function  of 272 

Peculiarity  of  s|>lenic  artery 272 

Spore  or  sponinjfiuni 376 

Stammttrin^' 374 

Starvation 131 

Starcli 23 

Physical  appearance  of 23 

Conversion  of  into  sugar 25 

Function  of 25 

Test  for 25 

Stearins 29 

SteatozUon  folliculoruui 121 

Stereorine 157 

Stoniacl) 108 

Mucous  membrane  of    108,  139 

Follicles  of 108,  139 

Movements  of 144 

Sudoriferous  glands 121 

Sugars 26 

Function  of 26 

Tests  for 27 

Supra-renal  ca))sules 273 

Structure  of 273 

Function  of 274 

Disease  of 274 

Suspensory  li^rament  of  lens 314 

Symj)atbc"tie  system 270,  330 

Nerves  of 286,  289,  336 

Function  of 337 

Division  of 338 

Synovial  membranes 102 

Structure  of 103 

Synovia 102 


I'AOK. 


Tactile  corjjusclcs 116, 

Taste,  sense  of 

Taste  goblets 


Tea 

Teeth 79, 

Structure  of .... 

Development  of 

Kruption  of 

Temperature  of  the  body 

in  disease 

of  animals 

how  produced 

Regulation  of 

Influence  of  nerves 

Sense  of 

Tendons 

Attachment  of 

Tesselated  epithelium 

Tests— 

'1  rommers' 

Fehling's  liquor  test 

Fermenlatitm 

Toniliu 

Moore's 

Iodine  test 

OniclinV  bile  test 

Pettenkofcr's 

Thalanii  optici 

Thirst 

Thymus  gland 

Structure  of 

Function  of 

Thyroid  gland 

Structure  of 


286 

304 

365 

129 

132 

79 

80 

82 

244 

244 

244 

245 

247 

246 

369 

60 

87 

97 

27 

27 

28 

28 

28 

25 

153 

153 

324 

131 

274 

274 

275 

275 


Thyroid  gland.  Function  of 

Tissues 

Attractive  or  selective  power  of.. . . 

Tissue  cement 

Tobacco 

Tongue 133, 

Papllhu  of 

Touch,  sense  of 

Transference  of  nervous  impressions... 
Trifacial  nervi' 

Division  of 

Irritation  of 

Trochlear  or  pathetic  nerve 

True  generation 

Tuber  annulare 

Tubes  of  Ilenle 

Tynii)anum 

Air  in 

Tymi)anitea 

IT 

Umbilicus,  anmiotic 

Umbilical  vesicle 

Cord 

Unconscious  cerebration 

Urachus 

Urine 

Secretion  of 

Specific  gravity  of 

Chemical  composition  of 

Urea 

Uric  or  litliic  acid •. 

Hippuric  acid 

Creatine 

Creatinine 

Salts  of 

I'rosaciiie  or  urochronie 45, 

Acid  fermentation  of 

Alkaline  fermentation  of 

Uterus,  preparation  for  ovum 

Involution  of 82, 

Muscular  fibre  cells  of 32, 


276 
60 
224 
6:5 
130 
3(i5 
106 


Valvuhe  Conniveiites.. 
Vasomotor  nerves  .. .. 

centre 

Vasa  VHsonim 

Vasa  deferentia 

Veins 


Structure  of 

Valves  of 

Circulation  In 

Velocity  of  circulation  In 

Ventricles  of  the  larynx 341, 

Ventrilo(iuism 

Vernix  Caseosa 

Vestibule 

Vice,  solitary 

Villi  (if  intestine 110, 

Struiture  of 

Absorpt  ion  by 

of  chorion  . .'. 

Vis  ii  tergc > 

Vis  nervosa 

Visceral  plates  , 

Vislim,  ))iienomena  of 

Circle  or  field  of 

Anule  of 

Defects  of 

Vital  elements  of  the  blood 

Vital  capacity  of  the  chest 


294 
331 
3:52 
332 
331 
376 
30(> 
258 
3r.H 
•MVi 
157 


3s7 
385 
391 
323 
403 
200 
259 
260 
261 
261 
202 
263 
264 
264 
264 
204 
265 
2(itJ 
389 
3i>2 
392 


109 
219 
306 
214 
402 
219 
219 
220 
220 
225 
370 
374 
121 
360 
378 
168 
111 
165 
388 
220 
296 
385 
361 
354 
352 


188 

2:6 


*9 


416 


INDEX. 


Taoe. 

Vitelline  membrane H79 

Vitelline  spheres 382 

Vitreous  humor 349 

A'ocal  cords 370 

Voice 370 

Tones  of  voice 372 

Compass  of Si 3 

Modifications 374 

Voluntary  attention 322 

Vomitiuff ,  mechanism  of 138 

Vowels  and  Consonants 374 

VV 

Warm-blooded  animals 244 

Water 16 

Function  of 16 

Whartonian  Jelly 71,  302 

White  fibrous  tissue GO 

Appearance  and  properties  of til 


Paok. 

White  fibrous  tissue,  Development  of . .     63 

White  blood  corpuscles 173 

Amueboid  movements  of 58,  173 

Function  of 196 

White  substance  of  Schwann ""l 

Will,  power  of >.^ 278,  322 

Willis,  circle  of 217,  317 

Wolrtian  bodies 401 

Y 

Yawning 238 

Yolk 279 

Yellow  elastic  tissue 62 

A|)pearance  and  properties  of 62 

Development  of 63 

Z 

Zona  pelludida 379 


mma 


Page. 

nientof..  63 

173 

58,  173 

196 

-l 

,....278,  322 

217,  317 

401 

238 

279 

62 

iS  of 62 

63 


...  379 


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PUBLISHED  BY 

.     LINDSA  Y  &  BLAKIS  TON,  Philadelphia, 
AITKEN  (WILLIAM),  M.  D., 

Professor  of  Pathology  lii  the  Army  Medical  School,  &€• 

THE  SCIENCE  AND    PRACTICE  OF   MEDICINE.     THIRD 

American,  from  the  Sixth  London  Edition.  Thoroughly  Revised, 
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u  work  of  reference. 


ALLINGHAM  (william),  F.  R.  C.  S., 

Surgeon  to  St.  Mark's  Hospital  for  Fistula,  &c. 

FISTULA,  HEMORRHOIDS,  PAINFUL  ULCER,  STRICT- 
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and  Treatment.     Third  Edition,  Revised  and  Enlarged  by  the  Author. 

This  book  has  been  well  received  by  the  Profession  ;  the  first  edition  sold  rap- 
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ft: 

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6 
ATTHILL  (lombe),  M.  D., 

Fellow  and  Examiner  in  Midwifery,  King  and  Queen's  College  of  Physicians,  Dublin. 

CLINICAL  LECTURES  ON  DISEASES  PECULIAR  TO  WO- 
MEN.  Fifth  Edition,  Revised  and  Enlarged,  with  numerous  Illustra- 
tions.    Price  .         .         .         .         .         .         .         .         .     $2.25 

The  value  and  pomilarity  of  this  book  is  proved  by  the  rajjid  sale  of  the  first  edition, 
which  wiiH  exiiaustud  in  h'ss  than  a  year  from  the  time  of  its  j)iil)licatioii.  It  appears  to 
possess  three  m'reat  merits  :  First,  It  treats  of  tlie  disea.ses  very  common  to  females.  Second, 
It  treats  of  them  in  a  thoroui;hly  elinieal  and  jmietical  manner.  Tliird,  Jt  is  concise,  orig- 
inal, an<l  illustrated  by  nunn-rous  eases  from  tlie  author's  own  exnerienee.  His  style  is  clear 
and  the  volume  is  the  result  of  tiie  author's  lar-^e  and  neeurate  clinical  observation  reeorde* 
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a  practical  guide  to  the  student  aud  practitioner.  —  Jiritiah  medical  Jouniul. 


ADAMS  (WILLIAM),  F.  R.  C.S., 

Surgeon  to  the  Royal  Orthopedic  and  Great  Northern  Hospitals. 

CLUB-FOOT:  ITS  CAUSES,  PATHOLOGY,  AND  TREAT- 
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ADAMS  (ROBERT),  M.  D., 

Regius  Professor  of  Surgery  in  the  University  of  Dublin,  &.C.,  &.c, 

RHEUMATIC  GOUT,  or  CHRONIC  RHEUMATIC  ARTHRI- 
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numerous  Woodcuts,  and  a  quarto  Atlas  of  Plates.  2  Volumes. 
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ALTHAUS  (JULIUS),  M.D., 

Physician  to  the  Infirmary  of  Epilepsy  and  Paralysis. 

A  TREATISE  ON  MEDICAL  ELECTRICITY,  Theoretical  and 
Practical,  and  its  Use  in  the  Treatment  of  Paralysis,  Neuralgia,  and  other 
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In  this  work  both  thescientifie  and  practical  aspects  of  the  subject  are  ably,  concisely,  and 
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in  the  English  language.  —  JYew  York  Medical  Record. 


ARNOTT  (henry),  F.R.C.S. 

CANCER:  its  Varieties,  their  Histology  and  Diagnosis. 
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With  Five 
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Professor  of  Surgery  in  the  University  of  Pennsylvania. 

TH      LACERATIONS  OF  THE  FEMALE  PERINEUM.  AND 

VESICO-VAGINAL    FISTULA,  their  History  and  Treatment,  with 

numerous  Illustrations.      Octavo.     Price  ....      $1.50 

Prof.  A      ^w  has  been  a  most  indefatigable  laborer  in  this  department,  and  his  work  stands  j 
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lansi  Dublin. 

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lumerous  lUustra- 
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3  of  the  first  edition, 
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cc.  His  style  is  ckiir 
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lumal. 


tals. 

\ND    TREAT' 

Royal  College  of 

h  106  Illustrations 

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THE  FUNCTIONS  AND  DISORDERS  OF  THE  REPRODUC- 
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author.  —  British  and  Foreiijn  Medico- L'kiruryical  lieview. 


I 


AVELING  (j.  il),  M.  D., 

Physician  to  Chelsea  Hospital  for  Diseases  of  Womeiii 

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LC,   &.Ci 

.TIC  ARTHRI- 

n.  Illustrated  by 
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ire  ably,  concisely,  and 
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Professor  of  Clinical  Medicine  in  the  University  of  Glasgow,  &c. 
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K>« 

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to*—— 

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Professor  of  Chemistry  at  St.  Thomas's  Hospitab 

NOTES    FOR   STUDENTS   IN    CHEMISTRY.     Compiled  from 
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BY  SAME  AUTHOR, 

THE    STUDENT'S    GUIDE    TO     MEDICAL    CHEMISTRY. 

With  Illustrations.     Preparing. 


^ffl 


c 
c 

I 

s 

: 
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BEALE  (LIONELS.),  M.D. 

DISEASE  GERMS:  AND  ON  THE  TREATMENT  OF  DIS- 
EASES CAUSED  BY  THEM. 

Part      L  — SUPPOSKD  NATURE  OF  DISK.\SE  GERMS. 
Pakt    IL— heal  nature  of  DIHKASE  (iElliMS. 

Pakt  in. -the  destruction  of  dise.\se  germs. 

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This  now  edition,  besides  incltidin),'  the  coiitentH  revined  and  enhir<i;ed  of  the  two  former 
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BIOPLASM.  A  Contribution  to  the  Physiology  of  Life,  or  an  Intro- 
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Part  I.  DISSENTIENT.      Part  II.  DEMONSTRATIVE.'    Part  III.  SUGGESTIVE. 

HOW  TO  WORK  WITH  THE  MICROSCOPE.  Fourth  Edition, 
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Octavo.     Price     .........     ^10.00 

THE  USE  OF  THE  MICROSCOPE  IN  PRACTICAL  MEDI- 
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500  Illustrations.     Octavo.       Much  enlarged.     Price       ,         .     ;^7.5o 


BLOXAM  (c.  l.), 

Professor  of  Chemistry  in  King's  College,  Londotii 
CHEMISTRY,    INORGANIC   AND    ORGANIC.      With  Experi- 
ments and  a  Comparison  of  Equivalent  and  Molecular  Formulae.     With 
276  Engravings  on  Wood.       Third  London  Edition,  revised.    Octavo. 
Price,  in  cloth,  $4.00  ;  leather, $5-°° 

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LABORATORY  TEACHING;  OR  PROGRESSIVE  EXER- 
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SIT  OF  DIS- 

MS. 

AS. 

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ife,  or  an  Intro- 
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icplainingthe  nature 
d  peculiar  to  living 

•d  Edition,  very 

ed   Plates.     One 

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avo.   Price 

nitains  a  full  descrip- 
ing  objects  under  the 

"S,  AND  CAL- 

Diagnosis,  and 
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Edition.      With 
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9 

BENNETT  (j.  henry),  M.  D. 

NUTRITION  IN  HEALTH  AND  DISEASP:.  A  Contribution 
to  Hygiene  and  to  Clinical  Mtilicine.  Third  Edition,  Revised  and 
Enlarged.     Octavo.  .  Cloth.     Price $2.50 

BY  SAME  AUTHOR. 
THE  TREATMENT  OF   PULMONARY  CONSUMPTION   BY 
HYGIENE,  CLIMATE,  AND  MEDICINE.     With  an  Appendix  on 
the  Sanitaria  of  the  United  States,  Switzerland,  and  the  Halearic  Isl- 
ands.    The  Third  Eilition,  much  Enlarged.     Octavo.     Price    .   $2.50 

BUCKNILL(joHN  CHARLE.S),  M.D.,  &  TUKE  (daniel  h.),M.D. 

A  MANUAL  OF  PSYCHOLOGICAL  MEDICINE:  containing  the 
Lunacy  Laws,  the  Nosology,  CEtiology,  Statistics,  Description,  Diagno- 
sis, Pathology  (including  Morbid  Histology),  and  Treatment  of  Insanity. 
Fourth  Edition,  much  enlarged,  with  Ten  Lithographic  Plates,  and  nu- 
merous other  Illustrations.     Octavo.     Preparing. 

This  edition  will  contain  a  number  of  pairea  of  ndditiniial  matter,  and,  in  consequence  of 
recent  advances  in  Psycholo<,'ical  Medicine,  several  chapters  will  be  rewritten,  bringing  the 
Classification,  Pathology,  and  Treatment  of  insiuiity  up  to  the  j)resent  time. 


~*c*- 


BROWNE  (j.  II.  BALFOUR),  Esq. 

MEDICAL  JURISPRUDENCE  OF  INSANITY.  Second  Edition, 
very  much  Enlarged.  With  References  to  the  Scotch  and  American 
Decisions,  etc.,  etc.     Octavo.     Price      .....     $5.00 

BIDDLE  0^>i'n"b.),  M.  D., 

Professor  of  Materia  Medlcaand  Therapeutics  in  the  Jefferson  Medical  College,  Philadelphia,  &c. 

MATERIA  MEDICA,  FOR  THE  USE  OF  STUDENTS.  With 
Illustrations.      Eighth  Edition,  Revised  and  Enlarged.     Price     ;^4.oo 

This  new  and  thoroughly  revised  edition  of  Professor  Riddle's  work  has  incorporated  in 
it  all  the  improvements  as  adopted  by  the  New  United  States  Pharmacopceiajust  issued.  It 
is  designed  to  present  the  leauing  facts  and  prineijjles  usually  comprised  under  this  head  as 
set  forth  by  the  standard  authorities,  and  to  nil  a  vacuum  which  seems  to  exist  in  the  want 
of  an  elementary  work  on  the  subject.  The  larger  works  usually  recommended  as  tc.Kt-books 
in  our  Medical  schools  are  too  voluminous  for  convenient  use.  'ibis  will  be  found  to  contain, 
in  a  condensed  form,  all  that  is  most  valuable,  and  will  supply  students  with  a  reliable  guide 
to  the  course  of  lectures  on  Materia  Medica  as  delivered  at  the  various  Medical  schools  in 
the  United  States. 

balfourTgTw.),  m.  d., 

Physlcrn  to  the  Royal  Infirmary,  Edinburgh  |  Lecturer  on  Clinical  Medicine,  &c. 

CLINICAL  LECTURES  ON  DISEASES  OF  THE  HEART  AND 
AORTA.     With  Illustrations.     Octavo.     Price       .         .         .     $4.00 

BYFORD  (v^),  A.M.,  M.D., 

Professor  of  Obstetrics  and  Diseases  of  Women  and  Children  in  the  Chicago  Medical  College,  &c. 

PRACTICE  OF  MEDICINE  AND  SURGERY.  Applied  to  the 
Diseases  and  Accidents  incident  to  Women.  Second  Edition,  Revised 
and  Enlarged.     Octavo.     Price 

SAME  AUTHOR. 
ON  THE  CHRONIC  INFLAMMATION  AND  DISPLACEMENT 
OF  THE  UNIMPREGNATED  UTERUS.     A  New,  Enlarged,  and 
Thoroughly  Revised  Edition,  with  Numerous  Illustrations.   8vo.    ^2.50 

Dr.  Byford  writes  the  exact  present  state  of  medical  knowledge  on  the  subjects  presented; 
and  does  this  so  clearly,  so  concisely,  so  truthfully,  and  so  completely,  that  liis  book  on  the 
uterus  will  always  meet  the  approval  of  the  profession,  and  be  everywhere  regarded  as  a 
popular  standard  work.  —  Buffalo  Medical  and  Surgical  Journal. 


c 
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10 

BLACK  (d.  camprkll),  M.  D., 

L.  R.  C.  S.  Edinburgh,  Member  of  the  General  Council  of  the  University  of  Glasgo*' ,  Lc,  Lc, 

THE  FUNCTIONAL  DISEASES  OK  THE  RENAL.  URINARY, 

and  Reproductive  Organs,  with  a  General  View  of  Urinary  Pathology. 

Prite $2.00 

The  stylo  <»f  th«  author  is  clonr,  ensy,  niid  ftprrcnhh*,  .  .  .  his  work  is  a  valuable  contri- 
bution to  medical  .scionce,  an<l  bcini;  pcniuMl  in  tliatdispoNition  of  unpn-Judiued  pi'.ilosophical 
inquiry  which  should  always  ^nide  a  true  physician,  admirably  cuibodien  the  spirit  of  '" 
opening  quotutiou  from  I'rolessor  Huxley,  —  Philada.  Med,  Times. 


A'  ita 


BY  SAME  AUTHOR. 

LECTURES  ON   BRIGHTS    DISEASE  OF  THE  KIDNEYS. 

Delivered  at  the  Royal  Infirmary  of  Glasgow.     With  20  Illustrations, 
engraved  on  Wood.     One  volume,  octavo,  in  Cloth.     Price     .     $1.50 


BENTLEY  and  TRIMEN'S 

MEDICINAL  PLANTS.  A  New  Illustrated  Work,  now  Publish- 
ing in  Monthly  Parts.  Thirty-seven  Parts  now  ready.  Eight  Colored 
Plates  in  each  Part.     Price,  each,  ......     52.00 

This  work  includes  full  botanical  descriptions,  and  an  account  of  the  properties  and  uses 
of  the  principal  idanls  employed  in  medicine,  especial  attention  bciiij^  paid  to  those  wiiich 
arc  otticinal  in  tiie  Hritish  and  United  States  Pliarmacopa'ias.  The  plants  which  supply 
food  and  substances  required  by  the  sick  and  convalescent  will  be  also  included.  Each  spe- 
cie!) will  be  illustrated  by  a  colored  plate  drawn  from  nature. 


BEASLEY  (henry). 

THE  BOOK  OF  PRESCRIPTIONS.  Containing  over  3000 
Prescriptions,  collected  from  the  Practice  of  the  most  Eminent  Physi- 
cians and  Surgeons — English,  French,  and  American  ;  comprising  also 
a  Compendious  History  of  the  Materia  Medica,  Lists  of  the  Doses  of  all 
Officinal  and  Established  Preparations,  and  an  Index  of  Diseases  and 
their  Remedies.     Fifth  Edition,  Revised  and  Enlarged.     Price     $2.25 

BY  SAME  AUTHOR. 

THE  POCKET  FORMULARY:  A  Synopsis  of  the  British  and 
Foreign  Pharmacopoeias.     Tenth  Revised  Edition.     Price       .     $2.25 

THE  DRUGGIST'S  GENERAL  RECEIPT  BOOK  and  VETERI- 
NARY FORMULARY.    Eighth  Edition.     Just  Ready.    Price,  $2.25 


BIRCH  (s.  B.),  M.  D., 

Member  of  the  Royal  Colleg'  of  Physicians.  &c. 
CONSTIPATED  BOWELS;  the  Various  Causes  and  the  Different 
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BRAUNE— BELLAMY. 

A^'  ..S  OF  TOPOGRAPHICAL  ANATOMY.  After  Plane 
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g,raphic  Plates  and  numerous  other  Illustrations  on  Wood.  By  Wilhelm 
Braune,  Professor  of  Anatomy  in  the  University  of  Leipzig.  Trans- 
lated and  Edited  by  Edward  Bellamy,  F.  R.  C.  S.,  Senior  Assistant  Sur- 
geon to,  and  Lecturer  on  Anatomy  and  Teacher  of  Operative  Surgery 
at,  the  Charing  Cross  Hospital,  London.  A  large  quarto  volume. 
Price  in  cloth,  ^12.00  ;  half  morocco, ^14.00 


gOf,  &c.,  &c. 

.URINARY, 

ary  Pathology. 

$2.00 

a  vnlnable  contri- 
liced  philoNopliii'iil 
ea  tbti  Bpirit  of  itd 


KIDNEYS. 

o  Illustrations, 
'rice     .     $1.50 


now  Publish- 

Eight   Colored 

$2.00 

irnperties  and  uses 
aid  to  thiise  wliich 
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tluded.    liach  spe- 


ig   over   3000 

Eminent  Pliysi- 
comprising  also 
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Diseases  and 
Price     $2.25 


British  and 

ice       .     $2.25 
ND  VETERI- 
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1  the  Different 

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After  Plane 
ill-i)age   Photo- 

By  WiLHELM 

eipzig.  Trans- 
3r  Assistant  Sur- 
erative  Surgery 
quarto  volume. 
.     ^[14. 00 


11 

COHEN  (i.  sous).  M.D. 

Iflciureron  Larynifoscopy  and  Diseases  of  the  Throat  and  Ghent  In  JefTerion  Medical  Colle|i^e, 

ON  INHALATION.  ITS  Tlll-RAPKU  I ICS  AND  PRACTICE. 
Including  a  Description  of  the  Aj)paratus  employed,  &c.  With  Cases 
and  Illustrations.      A  New  Enlarged  Edition.     Price       .         .     $2.50 

SAME  AUTHOR. 
CROUP.     In  its  Relations  to  Tracheotomy.     Price         .         .    ^i.oo 

CARSON  (joskf'h),  M.D., 

Professor  of  Materia  Medica  and  Pharmacy  in  the  University. 

A  HISTORY  OF  THE  MEDICAL  DIT'ARTMENT  OF  THE 
UNIVERSITY  OK  PENNSYLVANIA,  from  its  Foundation  in  1765: 
with  Sketches  of  Deceased  Professors,  &c.       .  .         .  .      552.00 


CHARTL:RLS  (mathew),  m.  d., 

Member  of  Hospital  Staff  and  Pr.  fessor  in  University  of  Glasgow. 

STUDENTS'  HAND-BOOK  OF   THE   PRACTICE  OF 
CINE.     With  Microscopic  and  other  Illustrations.     Price 


MEDI- 

$2.00 


Tills  hook  forms  one  volume  of  the  Students'  Guide  Series,  or  Text-Books,  uow  in  course 
of  publiculiou. 

CARPENTER  (w.  b.),  M.D.,  F.R.S. 

THE  MICROSCOPE  AND  ITS  REVELATIONS.  The  Fifth 
London  Edition,  Revised  and  Enlarged,  with  more  than  500  Illustra- 
tions        $5-oo 

CORR  (l.  h.),  M.D. 

OBSTETRIC    CATECHISM,  or  Obstetrics   reduced  to  Questions 

and  Answers.     With  Numerous  Illustrations.     Price         .  .     jg2.oo 

CHAVASSE  (p.  henry),  F.R.C.S,, 

Author  of  Advice  to  a  Wife,  Advice  to  a  Mother,  &c. 

APHORISMS  ON  THE  MENTAL  CULTURE  AND  TRAIN- 
ING OF  A  CHILD,  and  on  various  other  subjects  relating  to  Health 
and  Happiness.     Addressed  to  Parents.     Price         .         .         .     51.00 

Dr.  Chavasse's  works  have  been  very  favorably  received  and  had  a  large  circulation,  the 
value  of  his  advice  to  WIVES  and  MOTHKItS  having  thus  been  very  generally  recognized. 
This  book  is  a  sequel  or  companion  to  them,  and  it  will  be  found  both  valuable  and  important 
to  all  who  have  the  cure  of  families,  and  who  want  to  bring  Uj>  their  children  to  become  useful 
men  and  women.     It  is  full  of  fresh  thoughts  and  graceful  illustrations. 


CLARKE  (w.fairue),  M.D., 

Assistant  Surgeon  to  Charing  Cross  Hospital. 

CLARKE'S   TREATISE  ON  DISEASES   OF  THE  TONGUE. 

With  Lithographic  and  Wood-cut  Illustrations.     Octavo.'    Price  ;J!4.5o 

It  contains  The  Anatomy  and  Physiology  of  the  Tongue,  Importance  of  its  Minute  Exam- 
ination, Its  Congenital  Defects,  Atrophy,  Hypertro]>hy,  Parasitic  Diseases,  Inflammation, 
Byphilis  and  its  effects,  Various  Tumors  to  which  it  is  subject,  Accidents,  Injuries,  &c.,  &c. 

COOPER  (s.). 

A  DICTIONARY  OF  PRACTICAL  SURGERY  AND  ENCY- 
CLOPEDIA OF  SURGICAL  SCIENCE.  New  Edition,  brought 
down  to  the  present  time.  By  Samuel  A.  Lane,  F.R.C.S.,  assisted  by 
other  eminent  Surgeons.    In  two  vols.,  of  over  1000  pages  each.    ^12.00 


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12 

CLAY  (cHARLES),  M   D. 

Fellow  of  the  London  Obstetrical  Society,  kc, 

THE  COMPLETE  HAND-BOOK  OF  OBSTETRIC  SURGERY, 

or,  Short  Rules  of  Practice  in  Every  Emergency,  from  the  Simplest  to 
the  most  Formidable  Operations  in  the  Practice  of  Surgery.  First 
American  from  the  Third  London  Edition.  With  numerous  Illustra- 
tions.    In  one  volume.  ;^2.oo 

CHAMBERS  (thomas  k.),  M.  D., 

LECTURES,  CHIEFLY  CLINICAL.  Illustrative  of  a  Restorative 
System  of  Medicine. 

CORMACK  (sir  john  i^^^K.  B.,  F.  R.  S.  E.,  M.  D. 

Edinburgh  and  Paris,  Fellow  Royal  College  of  Physicians,  Physician  to  the  Hertford  British  Hospital,  Paris,  &c. 

CLINICAL  STUDIES,  Illustrated  by  Cases  observed  in  Hospital  and 
Private  Practice.    With  Illustrative  Plates.    2  Volumes.    Octavo.      $5.00 

. KX 

COBBOLD  (t.  spencer),  M.D.,  F.R.S. 
WORMS:  a  Series  of  Lectures  delivered  at  the  Middlesex  Hospital 
on  Practical  Helminthology.     Post  Octavo ^i-75 

. to* 

CLEAVELAND  (c.  h.),  M.D., 

Member  of  the  American  Medical  Association,  &.c, 

A  PRONOUNCING  MEDICAL  LP:XICON.  Containing  the  Cor- 
rect Pronunciation  and  Definition  of  Terms  used  in  Medicine  and  the 
Collateral  Sciences.     Improved  Edition,  Cloth,     $1.00;  Tucks,    ^1.25 

This  work  is  not  only  a  Lexicon  of  all  the  words  in  common  use  in  Medicine,  but  it  is 
also  a  Pronouncing  Dictionary,  a  feature  of  great  value  to  Medical  Students.  To  the  Dis- 
penser it  will  prove  an  excellent  aid,  and  also  to  the  Pharmaceutical  Student.  It  has  received 
strong  commendation  both  from  the  Medical  Press  and  from  the  profession. 


COLES  (oakley),  D.D.S. 

Dental  Surgeon  to  the  Hospital  for  Diseases  of  the  Throat,  &c. 

A  MANU/iL  OF  DENTAL  MECHANICS.  Containing  much 
information  of  a  Practical  Nature  for  Practitioners  and  Students. 

INCLUDING 
The  Preparation  of  the  Mouth  for  AfLificial  Teeth,  on  Taking  Impressions,  Various 
Modes  of  Applying  Heat  in  the  Lal)ori,tory,  Casting  in  Plaster  of  Paris  and  Metal, 
Precious  Metals  used  in  Dentistry,  Making  Gold  Plates,  Various  Forms  of  Porcelain 
used  in  Mechanical  Dentistry,  Pivot  Teet'.i,  Choosing  and  Adjusting  Mineral  Teeth,  the 
Vulcanite  Base,  the  Celluloid  Base,  Treatment  of  Deformities  of  the  Mouth,  lleeei])ts 
for  Making  Gold  Plate  and  Solder,  etc.,  etc. 
With  140  Illustrations.     Price $2.00 

SAME  AUTHOR. 

ON  DEFORMITIES  OF  THE  MOUTH,  CONGENITAL  AND 
ACQUIRED,  with  their  Mechanical  Treatment.  Second  Edition,  Re- 
vised and  Enlarged.     With  Illustrations.     Price,     .         .         . 


DOMVILLE  (EDWARD  ;.),  M.  D. 

A  MANUAL  FOR  HOSPITAL  NURSES  and  Others  engaged  in 
Attending  the  Sick.     i2mo.     Price         .         .         .         .         .     ;^i.oo 


:  SURGERY, 

the  Simplest  to 

Surgery.     First 

nerous  Illustra- 

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ish  Hospital,  Paris,  &,c. 

n  Hospital  and 
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lesex  Hospital 
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aining  the  Cor- 
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Medicine,  but  it  is 
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iit.    It  has  received 


itaining   much 

Students. 

ipressions,  Various 
Paris  and  Metal, 
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lie  Mouth,  lleceijjts 

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nd  Edition,  Re- 


18 

CLARK  (f.  le  gros),  F.  R.  S., 

Senior  Surgeon  to  St.  Thomas's  Hospital.  • 

OUTLINES  OF  SURGERY  AND  SURGICAL  PATHOLOGY, 
including  the  Diagnosis  and  Treatment  of  Obscure  and  Urgent  Cases, 
and  the  Surgical  Anatomy  of  some  Important  Structures  and  Regions, 
Assisted  by  W.  W.  Wagstaffe,  F.  R.  C.  S.,  Resident  Assistant-Surgeon 
of,  and  Joint  Lecturer  on  Anatomy  at,  St.  Thomas's  Hospital.  Second 
Edition,  Revised  and  Enlarged.     Price  ....     ^2.00 


COTTLE  (E.  wyndham),  M.  A.,  F.  R.  C.  S.,  &c. 

THE  HAIR  IN  HEALTH  AND  DISEASE.  Partly  from  Notes 
by  the  late  George  Navler,  F.  R.  C.  S.,  Surgeon  to  the  Hospital  for 
Diseases  of  the  Skin,  &c.     i8mo.     Cloth.     Price        .         .         $0.75 

CURLING  (t.  b.),  F.R.S., 

Consulting  Surgeon  to  the  London  Hospital,  Lc, 

A  PRACTICAL  TREATISE  ON  THE  DISEASES  OF  THE 
TESTIS  AND  OF  't^hE  SPERMATIC  CORD  AND  SCROTUM. 
Fourth  Revised  and  Enlarged  Edition.     Octavo.     Price.         .     $$-50 

BY  SAME  AUTHOR. 

OBSERVATIONS  ON  DISEASES  O^/  THE  RECTUM.  With 
Illustrations.  Fourth  Edition,  Revised  and  Enlarged.  Octavo.  Cloth. 
Price $2.75 


CAZEAUX  (p.).  M.  D., 

Adjunct  Professor  of  the  Faculty  of  Medicine,  Paris,  etc. 

A  THEORETICAL  AND  PRACTICAL  TREATISE  ON  MIDWIFERY, 

including  the  Diseases  of  Pregnancy  and  Parturition.     Translated  from 

the  Seventh  French  Edition,  Revised,  Greatly  Enlarged,  and  Improved, 

by  S.  Tarnier,  Clinical  Chief  of  the  Lying-in  Hospital,  Paris,  etc., 

with  numerous  Lithographic  and  other  Illustrations.     Price,  in  Cloth, 

^6.00;  in  Leather         ........      ;^7-oo 

M.  Cazeaux's  Great  Work  on  Obstetrics  has  become  classical  in  its  character,  and  almost 
an  Encyclopifidia  in  Its  fulness.  Written  expressly  for  the  use  of  students  of  medicine,  its 
teachin.i^s  are  plain  and  explicit,  presenting  a  condensed  summary  of  the  leading  principles 
established  by  the  musters  of  the  obstetric  art,  and  such  clear,  practical  directions  for  the 
management  of  the  pregnant^  ])arturient,  ami  pueriieral  states,  as  have  been  sanctioned  by 
the  motit  authoritative  practitiouers,  and  confirmed  by  the  author's  own  experieuce. 


ers  engaged  in 
.     $1.00 


DOBELL  (HORACE),  M.D., 

Senior  Physician  to  tdo  Hospital. 

WINTER  COUGH  (CATARRH,  BRONCHITIS,  EMPHYSEMA, 
ASTHMA).  Lectures  Delivered  at  the  Royal  Hospital  for  Diseases  of 
the  Chest.  The  Third  Enlarged  Edition,  with  Colored  Plates.  Octavo. 
Price $350 

BY  SAME  AUTHOR. 

ON  LOSS  OF  WEIGHT,  BLOOD-SPITTING,  AND  LUNG 
DISEASE.  Witii  a  Colored  Frontispiece  of  the  Lung,  a  Tabular  Map, 
&c.,  &c.     Octavo.     Cloth.     Price         .         .         .         .         •     $3-^5 


c 

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14 
DIXON  (jAMEs),  F.R.C.S.     ■ 

Surgeon  to  the  Royal  London  Ophthalmic  Hospital,  &c. 

A  GUIDE  TO  THE  PRACTICAL  STUDY  OF  DISEASES  OF 

THE  EYE,  with  an  Outline  of  their  Merlical  and  Operative  Treatment, 

with  Test  Types  and  Ilhistrations.     Third  Edition,  thoroughly  Revised, 

and  a  great  portion  Rewritten.     Price ;^2.oo 

Mr.  Dixon's  hook  is  essentially  a  practical  one,  written  by  an  observant  author,  who  brings 
to  his  special  subject  a  souud  knowledge  of  general  Medicine  and  Surgery. — Dublin  Quarterly. 


DILLNBERGER  (dr.  emil). 

A  HANDY-BOOtC  OF  THE  TREATMENT  OF  WOMEN  AND 

CHILDREN'S  DISEASES,  according  to  the  Vienna  Medic-1  School. 

Part  I.  The  Diseases  of  Women.      Part  II.   The  Diseases  of  Children. 

Translated    from   the    Second    German  Edition,  by  P.  Nicol,  M.  D. 

Price     .         .         .         .         .  .         .  .         .         .  .     ^1.50 

Many  practitioners  will  be  glad  to  possess  this  little  manual,  which  gives  a  large  mass 
of  practical  liints  on  the  treatment  of  disea.ses  which  probably  make  up  the  larger  lialf  of 
every-day  practice.  The  translation  is  well  made,  and  explanations  of  reference  to  German 
medicinal  preparations  are  given  with  proper  fulness.  —  Tlie  Practitioner. 


DUNGLISON  (RICHARD  j.),  M.  D. 

THE    PRACTITIONER'S  REFERENCE    BOOK.      Containing 

Therapeutic   and   Practical  Hints,  Dietetic   Rules  and   Precepts,   and 

other  General  Information  Useful  to  the  Physician,  Pharmacist,  and 

Student.     Octavo.     Cloth.  Price          .         .         .         .         •     $3-So 


r 


h 

ft;. 


DUCHENNE  (dr.  g.  b.). 

LOCALIZED  ELECTRIZATION  AND  ITS  APPLICATION 
TO  PATHOLOGY  AND  THERAPEUTICS.  Translated  by  Her- 
bert TiBBiTS,  M.D.     With  Ninety-two  Illustrations.     Price     .     $3.00 

Duchenne's  great  work  is  not  only  a  well-nigh  exhaustive  treatise  on  the  medical  uses  of 
Electricity,  but  it  is  also  an  elaborate  exposition  of  the  dilferent  diseases  in  which  Electric- 
ity has  proved  to  be  of  value  as  a  therapeutic  and  diagnostic  agent. 

Part  11.,  illustrated  by  chromo-lUhographs  and  numerous  wood-cuts,  is  preparing. 


DURKEE  (siLAs),  M.D., 

Fellow  of  the  Massachusetts  Medical  Society,  tiz, 

GONORRHCEA   AND    SYPHILIS.     The  Sixth  Edition,  Revised 

and  Enlarged,  with  Portraits  and  Eight  Colored  Illustrations.     Octavo. 

Price     .         .         •         .         .         .         .         .         .         .         •     $3-50 

Dr.  Durkee's  work  impresses  the  reader  in  favor  of  the  author  bv  its  general  tone,  the 
thorough  honesty  everywhere  evinced,  the  skill  with  whicli  tiu'  book  is  arranged,  the  man- 
ner in  wliidi  the  facts  arc  cited,  the  clever  way  in  which  the  author's  experience  is  brought 
in,  the  lucidity  of  the  reasoning,  and  the  care  with  which  the  therapeutics  of  venereal  com- 
plaints arc  treated. — Lancet. 


DRUITT  (ROBERT),  F.R.C.S. 

THE  SURGEON'S  VADE-MECUM.  A  Manual  of  Modern  Sur- 
gery. The  Eleventh  Revised  and  Enlarged  Edition,  with  369  Illus- 
trations.     Price     .         .         .         .         .         .         .         .         .     $5.00 


EASES  OF 

ve  Treatment, 

ighly  Revised, 

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ithor,  who  brings 
)ublin  Quarterly. 


)MEN  AND 

eclic"!  School. 

s  of  Children. 

NicoL,  M.  D. 

vcs  a  large  mass 
le  larger  lialf  of 
ereuce  to  Geruiau 


Containing 
Precepts,  and 
liarmacist,  and 

.     $3-50 


PLICATION 

ated  by  Her- 

rice     .     $3-oo 

medical  uses  of 
which  Electric- 

s  preparing. 


tion,  Revised 
ions.     Octavo. 

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general  tone,  the 

rranged,  the  man- 

■rienee  is  brought 

of  venereal  com- 


Modern  Sur- 
nth  369  lilus- 
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15 
DALBY  (w.  B.),  F.  R.  C.  S., 

Aural  Surgeon  to  St.  George's  Hospital. 

LECTURES  ON  THE  DISEASES  AND  INJURIES  OF  THE 
EAR.  Delivered  at  St.  George's  Hospital.  With  Illustrations. 
Price $150 

"We  cordially  recoinmcml  this  admirable  volume  by  Jlr.  Dalby  as  a  trustworthy  guide  in 
the  treatment  of  the  aH'eetions  of  the  ear.  The  book  is  moderate  in  |)riee,  beautii'iiUy  illus- 
trated by  wood  cuts,  and  got  up  in  the  best  style.  —  Glusyow  Medical  Journal. 


DAY  (wiLLi.\M  henry),  M.  D., 

Physician  to  the  Samaritan  Hospital  for  Women  and  Children,  &c. 

HEADACHES.   THEIR    NATURE.    CAUSES,  AND 
MENT.     Second  Edition.     i2mo.     Cloth.     Price 


TREAT- 

$2.00 


DUNGLISON  (robley),  M.  D., 

Late  Professor  of  Institutes  of  Medicine,  &c.,  in  the  Jefferson  Medical  College. 
A  HISTORY  OF  MEDICINE,  from  the  Earliest  Ages  to  the  Com- 
mencement of  the  Nineteenth  Century.     Edited  by  his  son,  Richard 
J.  DuNGLisoN,  M.  D $2.50 

ELLIS    (EDWARD),   M.  D., 
Physician  to  the  Victoria  Hospital  for  Sick  Children,  &c. 

A  PRACTICAL  MANUAL  OF  THE  DISEASES  OF  CHIL- 
DREN, with  a  Formulary.  Third  Enlarged  Edition,  Revised  and 
Improved.     One  volume.    .         .         .         .  .         .         .         g2.oo 

The  AUTUOR,  in  issuing  this  new  eflitiou  of  his  book,  says:  "I  have  very  carefully  revised 
each  chapter,  adding  several  new  sections,  and  making  considerable  additions  where  the 
Bubiects  seemed  to  reouire  fuller  treatment,  without,  however,  sacrificing  conciseness  or 
unduly  increasing  the  bulk  of  the  volume." 

FOTHERGILL  (j.  milner),  M.  D., 

Assistant  Physician  to  City  of  London  Hospital  for  Diseases  of  the  Chest,  die  ' 

THE  HEART,  ITS  DISEASES  AND  THEIR  TREATMENT, 

including  the  Gouty  Heart.  Second  Edition,  Entirely  Rewritten  and 
Enlarged,  with  Two  Full-Page  Lithographic  Plates  and  Forty  other 
Illustrations.     Octavo.     Price         ...... 

"  Dr.  Fothergill's  remarks  on  rest,  on  proi)er  blood  nutrition  in  Heart  Disease,  in  the 
treatment  of  Sequela;  of  it,  and  on  the  action  of  special  meilieines,  all  indicate  that  in  stiuly- 
ing  the  pathology  of  Heart  Disease,  he  has  earnestly  kept  in  view  the  best  means  of  mitigat- 
ing suti'eriug  and  of  prolonging  life."  —  Lancet. 

FOX   (CORNELIUS  B.),  M.  D. 

SANITARY  EXAMINATIONS  of  Water,  Air,  and  Food.     94  En- 
gravings.    8vo.     Price        .......        ^4.00 


FOX  (tilbury),  M.  D.,  F.  R.  C.  P. 

Physician  to  the  Department  for  Skin  Diseases  in  University  College  Hospital. 

ATLAS  OF  SKIN  DISEASES.  Consistin<,r  of  a  Series  of  Colored 
Illustrations,  in  Monthly  Parts,  together  with  Descriptive  Text  and 
Notes  upon  Treatment ;  each  Part  containing  Four  Plates,  reproduced  by 
Chromo-Lithography  from  the  work  of  Willan  &  Bateman,  or  taken  from 
Original  Sources.  iSIow  Complete  in  18  Parts.  Price,  per  Part,  $2.00  ; 
or  in  one  large  Folio  volume,  bound  in  cloth.     Price     .         .     $30.00 


16 


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c 

I 


f 


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FENNER  (c.  s.),  M.  D.,  &c. 

VISION:  ITS  OPTICAL  DEFECTS,  and  the  Adaptation  of  Spec- 
tacles; embracing  Physical  Optics,  Physiological  Optics,  Errors  of  Re- 
fraction and  Defects  of  Accommodation,  or  Oi)tical  Defects  of  the  Eye. 
With  74  Illustrations.  Selections  from  the  Test  Types  of  Jaeger  and 
Snellen,  etc.     Octavo.     Price $3-So 


FOSTER   (BALTHAZAR),   M.  D., 

Professor  of  Medicine  in  Queen's  College. 

LECTURES  AND  ESSAYS  ON  CLINICAL  MEDICINE.  Re- 
vised and  Enlarged  by  the  Author.  With  Engravings.  Octavo. 
Price     .         .       ^ $3.00 

FRANKLAND  (e.),  M.  D.,  F.  R.  S.,  &c. 

HOW  TO  TEACH  CHEMISTRY,  being  the  substance  of  Six 
Lectures  to  Science  Teachers.  Reported,  with  the  Author's  sanction, 
by  G.  George  Chaloner,  F.  C.  S.,  &c.     With  Illustrations         .     1^1.25 

FENWICK  (SAMUEL),  M.D.,  F.R.C.P. 

THE  MORBID  STATES  OF  THE  STOMACH  AND  DUO- 
DENUM, AND  THEIR  RELATIONS  TO  THE  DISEASES  OF 
OTHER  ORGANS.     With  Ten  Plates $4.25 


FLINT  (AUSTIN)  ,^M.D., 

Professor  of  the  Principles  and  Practice  of  Medicine,  &c.,  Bellevue  Hospital  College,  New  Yorki 

CLINICAL  REPORTS  ON  CONTINUED  FEVER.  Based  on 
an  Analysis  of  One  Hundred  and  Sixty-four  Cases,  with  Remarks  on 
the  Management  of  Continued  Fever;  the  Identity  of  Typhus  and 
Typhoid  Fever  j  Diagnosis,  &c.,  &c.     Octavo.     Price    .         .     ^2.00 


GANT    (FREDERICK  J.),  F.  R.  C.  S., 
Assisted  by  Drs,  Morrell,  Mackenzie,  Barnes,  Erasmus  Wilson,  and  other  Specialists. 

THE  SCIENCE  AND  PRACTICE  OF  SURGERY.  Second 
Edition.  1700  Pages.  1000  Illustrations.  2  Vols.  Price,  cloth,  $11.00; 
sheep $13.00 

DISEASES  OF  THE  BLADDER,  PROSTATE  GLAND,  AND 
URETHRA,  including  a  Practical  View  of  Urinary  Diseases,  Deposits, 
and  Calculi.  Fourth  Edition,  Revised  and  Enlarged.  With  New  Il- 
lustrations.    Now  Ready.     Price $3- 50 


-»o»- 


GODLEE  (r.  J.),  M.D.. 

Assistant-Surgeon  University  Ce'.lego  Hospitalt 

AN  ATLAS  OF  HUMAN  ANATOMY.  Illustrating  the  Anatomy 
of  the  Human  Body,  in  a  Series  of  Dissections.  Accompanied  by 
References  and  an  Explanatory  Text.  To  be  completed  in  Twelve  or 
Thirteen  Bi-monthly  Parts,  Folio  Size,  each  Part  containing  Four  large 
Colored  Plates,  or  Eight  Figures.  Seven  Parts  Now  Ready.  Price  per 
Part $2.50 


17 


ition  of  Spec- 
Errors  of  Re- 
els of  the  Eye. 
of  Jaeger  and 

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CINE.     Re- 

igs.      Octavo. 
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:c. 

tance  of  Six 
hor's  sanction, 
IS         .     $1.25 


AND    DUO- 
)1SEASES  OF 


$4-25 


ige.  New  York. 
^.     Based  on 
:h  Remarks  on 
f  Typhus   and 
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pecialistSi 

RY.     Second 

cloth,  $11.00; 
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AND,  AND 

uses,  Deposits, 
With  New  II- 

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the  Anatomy 
companied  by 
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ing  Four  large 
iy.  Price  per 
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GROSS  (SAMUEL  D.),  M.  D., 
Professor  of  Surgery  In  the  Jefferson  Medical  College,  Philadelphia,  etc. 

AMERICAN  MEDICAL  BIOGRAPHY  OF  THE  NINETEENTH 
CENTURY.  With  a  Portrait  of  Benjamin  Rush,  M.D.    Octavo.    $3.50 

GREENHOW  (e.  headlam),  M.  D., 

Fellow  of  the  Royal  College  of  Physicians,  etc. 

ON  CHRONIC  BRONCHITIS,  Especially  as  Connected  with  Gout, 
Emphysema,  and  Diseases  of  the  Heart.     Price      .         .         .     $1.50 

BY  SAME  AUTHOR. 

ADDISON'S  DISEASE.  Being  the  Cronian  Lectures  for  1875. 
Delivered  before  the  Royal  College  of  Physicians.  Revised,  and  Illus- 
trated by  numerous  Cases  and  5  full-page  Colored  Engravings.  One 
volume,  octavo.     Price  .         .         .         .         .         .         •         .     $3-°° 


HARLEY  (GEORGE),  M.  D.,  F.  R.  C.  P., 

_  Physician  to  University  College  Hospital. 

THE  URINE  AND  ITS  DERANGEMENTS:  With  the  Applica- 
tion of  Physiological  Chemistry  to  the  Diagnosis  and  Treatment  of 
Constitutional  as  well  as  Local  Diseases.  New  Revised  and  Enlarged 
Edition  preparing.      With  Engravings. 

We  have  here  a  valuable  addition  to  the  librrry  of  the  praetisiiiff  physician; 
not  only  for  the  information  wliieh  it  contains,  but  also  for  the  siij^gestive  way  in  which 
many  of  the  subjects  are  treated,  as  well  as  for  the  fact  that  it  contains  the  ideas  of  one  who 
thoroughly  believes  in  the  future  capabilities  of  Therapeutics  based  on  Physiological  tacts, 
and  iu  the  important  service  to  be  rendered  by  Chemistry  to  Physiological  investigation. 

American  Journal  of  the  Medical  Science. 


HEATH   (CHRISTOPHER),  F.  R.  C.  S., 

Surgeon  to  University  College  Hospital  and  Holme  Professor  of  Clinical  Surgery  in  University  CoHege. 
OPERATIVE  SURGERY.  Elegantly  Illustrated  by  20  Large  Col- 
ored Plates,  Imperial  Quarto  Size,  each  Plate  containing  several  Fig- 
ures, drawn  from  Nature  by  M.  Leveille,  of  Paris,  and  Colored  by  hand 
under  his  direction.  Complete  in  Five  Quarterly  Parts.  Price,  per  Part, 
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HEWITT  (graily),  M.  D., 

Physician  to  the  British  Lying-in  Hospital,  and  Lecturer  on  Diseases  of  Women  and  Children,  &c. 

THE   DIAGNOSIS,    PATHOLOGY,   AND    TREATMENT   OF 

DISEASES   OF   WO   .EN,  including   the   Diagnosis  of  Pregnancy. 

Founded  on  a  Course  of  Lectures  delivered  at  St.  Mary's  Hospital 

Medical  School.     The  Third  Edition,  Revised    and   Enlarged,  with 

new  Illustrations.     Octavo.     Price  in  Cloth         .         .         .         ;^4.oo 

"         Leather     .         .         .  5.00 

This  new  edition  of  Dr.  Hewitt's  book  has  been  so  much  modified,  that  it  may  be  considered 
Bubstantially  a  new  book ;  very  nnich  of  the  matter  has  been  entirely  rewritten,  and  the  whole 
work  ha-s  been  rearranged  in  such  a  manner  as  to  present  a  most  decided  improvement  over 
previous  editions.  Dr.  Hewitt  is  the  leading  clinical  teacher  on  Diseases  of  Women  in  liOndon, 
and  the  eharaeteristic  attention  jiaidto  Diagnosis  by  liiin  has  given  his  work  great  |io|)ularity 
there.  It  may  unquestional)ly  be  considered  the  most  valuable  guide  to  correct  Diagnosis  to 
be  fouud  in  the  English  language.  n 


18 


c 


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It 

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I 


HILLIER  (THOMAS),  M.D., 

Physician  to  the  Hospital  for  Sick  Chiidren,  &c, 

A  CLINICAL  TREATISE  ON  THE  DISEASES  OF  CHILDREN. 
Octavo.     Price      .........     $2.00 

Wc  havo  said  enough  to  indicate  and  illustrate  tho  excellence  of  Dr.  Ilillicr's  volume.  It 
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accuracy  and  sound  practice.  — London  jMitcct. 


HOLDEN  (luther),  F.R.C.S. 

HUMAN  OSTEOLOGY,  comprising  a  Description  of  the  Bones 
with  Delineations  of  the  Attachments  of  the  Muscles,  &c.  With 
numerous  Illustrations.     Fifth  Edition,  carefully  Revised.    Price,  1^5.50 

HOLDEN'S  MANUAL  OF  DISSECTIONS  OF  THE  HUMAN 
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HARRIS  (ciiAPiN  A.),  M.  D.,  D.  D.  S. 

Late  President  of  and  Professor  of  the  Principles  and  Practice  of  Dental  Surgery  in  tlie  Baltimore  Collegfe,  &c. 

THE  PRINCIPLES  AND  PRACTICE  OF  DENTAtRY.  Tenth 
Revised  Edition.  .  In  great  part  rewritten,  rearranged,  and  with  many 
new  and  important  Illustrations.  Including — i.  Dental  Anatomy  and 
Physiology.  2.  Dental  Pathology  and  Therapeutics.  3.  Dental  Sur- 
gery. 4.  Dental  Mechanics.  Edited  by  P.  H.  Austen,  M.D.,  Pro- 
fessor of  Dental  Science  and  Mechanism  in  the  Baltimore  College  of 
Dental  Surgery.  With  nearly  400  Illustrations,  including  many  new 
ones  made  especially  for  this  edition.  Royal  octavo.  Price,  in  cloth, 
^^6.50;  in  leather .     1^7.50 

This  new  edition  of  Dr.  Harris's  work  lias  been  thoroughly  revised  in  all  its  parts  —  more 
60  than  any  previous  edition.  Soyreut  have  been  the  advances  in  many  branelies  of  dentistry, 
that  it  wasi  found  necessary  to  rewrite  the  articles  or  subjects,  and  this  has  been  done  in  tiie 
most  efficient  manner  by  Professor  Austen,  for  many  years  an  associate  and  friend  of  Dr. 
Harris,  assisted  by  Proijisor  Gorgas  and  Thomas  tS.  Latimer,  M.D.  The  publishers  feel 
assured  that  it  will  now  be  found  the  most  complete  text-book  for  the  student  and  guide  for 
the  practitioner  iu  the  English  language. 

SAME  AUTHOR. 

A  DICTIONARY  OF  MEDICAL  TERMINOLOGY,  DENTAL 

SURCiERY,  AND  THE  COLLATERAL  SCIENCES.  Fourth  Edition, 

Carefully  Revised  and  Enlarged,  by  Ferdinand  J.  S.  Gorgas,  M.  D., 

D.D.S.,  Professor  of  Dental  Surgery  in  the  Baltimore  College,  &.c.,  &c. 

Royal  octavo.     Price,  in  cloth,  ^6.50;  in  leather  .         .         57-5o 

The  many  advances  in  Dental  Science  rendered  it  necessary  that  this  edition  should  be 
thoroughly  revised,  which  has  been  done  in  the  nuxt  satisfactory  manner  li  ''rofessor  Gorgas, 
Dr.  Harris's  successor  in  the  BaUin4()re  Dental  College,  lie  having  added  m  ;trly  three  tiiou- 
sand  new  words,  besides  making  many  additions  ami  corrections.  The  doses  of  the  more 
prominent  medicinal  agents  have  also  been  added,  and  in  every  way  the  book  has  been  greatly 
improved,  and  its  value  euhauced  as  a  work  of  reference. 


HABERSHON  (s.  o.),  M.  D.,  F.  R.  C.  R, 

Senior  Physician,  Guy's  Hospital. 

ON  DISEASES   OF  THE  ABDOMEN,  STOMACH,  and  Other 
Parts  of  the  Aliinentary  Canal.     Third  Edition.     8vo.     Price.    S5.00 


CHILDREN. 

;g2.oo 

iUier's  volume.     It 
cultivate  cliuical 


of  the  Bones 
les,  &c.  With 
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HE  HUMAN 

Price    • 
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altimore  Collee;ei  ic. 
TRY.  Tenth 
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il  Anatomy  and 
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lore  College  of 
:ling  many  new 
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all  its  parts  — more 
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Y,  DENTAL 

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ollege,  &:c.,  &c. 
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edition  should  be 

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>ok.  has  been  greatly 


I   P. 

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19 

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HARDWICH'S  MANUAL  OF  PHOTOGRAPHIC  CHEMISTRY. 
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HEADLAND  (f.  w.),  M.D., 

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ON  THE  ACTION  OF  MEDICINES  IN  THE  SYSTEM.     Sixth 

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ON  HEMATURIA  as  a  Symptom  of  Diseases  of  the  Genito-Uri- 
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HEATH  (Christopher),  F.R.C.S., 

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HUFELAND  (c.  w.),  M.D. 

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Attending  Surgeon  Pennsylvania  Hospital,  Slc, 

EARTH  AS  A  TOPICAL  APPLICATION  IN  SURGERY. 
Being  a  full  Exposition  of  its  use  in  all  the  Cases  requiring  Topical 
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HUTCHINSON  (Jonathan),  F.  R.  C.  S. 

Senior  Surgeon  to  tlie  London  Hospitaii 

ILLUSTRATIONS  OF  CLINICAL  SURGERY.  Consisting  of 
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Emeritus  Professor  In  tlie  University  of  Pennsylvania. 

HODGE     ON     FCETICIDK,    OR     CRIMINAL     ABORTION. 

Fourth  Edition.     Price,  in  paper,  30  cents  ;  in  cloth,  .  $0.50 

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Of  Newark,  New  Jersey. 
CONTAINING  THREE  HUNDRED  ILLUSTRATIONS. 
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•  •  •  •  •         v^n**     3 


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A  PRACTICAL  TREATISE  ON  AURAL  SURGERY, 
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JONES,  SIEVEKING,  and  PAYNE. 

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21 
JAMES  (prossek),  M.  D..  M.  R.  C.  P., 

Physician  to  Throat  Hospital. 
SORE  THROAT:  Its  Nature, Varieties,  and  Treatment,  and  its  Con- 
nection with  other  Diseases.    Third  Edition.     Colored  Plates.     i2mo. 
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JONES'  AURAL  ATLAS. 

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M.D.,  Surgeon  to  the  Cork  Ophthalmic  aiid  Aural  Hospital.  4to. 
Cloth.     Price $6.00 

LAWSON  (GEORGE),  F.R.C.S., 

Surgeon  to  the  Royal  London  Ophthalmic  Hospital. 

DISEASES  AND  INJURIES  OF  THE  EYE,  THEIR  MEDICAL 
AND  SURGICAL  TREATMENT.  Containing  a  Formulary,  Test 
Types,  and  Numerous  Illustrations.      Price       .         .         .         .     $2.00 

This  Manual  is  admirably  clear  and  eminently  }>  "ticnl.  The  reader  feels  that  he  is  in 
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to  be  positive,  is  so  from  the  fulness  of  knowledge  and  experience,  and  who,  while'well  jic- 
quiiinted  with  the  writings  and  labors  of  other  authorities  on  the  matters  he  treats  of,  haa 
himself  practically  worked  out  what  he  teaches.  —  Loudon  Medical  Tivies  and  Gazette, 

LEBER  &  ROTTENSTEIN  (drs.). 

DENTAL  CARIES  AND  ITS  CAUSES.  An  Investigation  into 
the  Influence  of  Fungi  in  the  destruction  of  the  Teeth,  translated  by 
Thomas  H.  Chandler,  D.M.D.,  Professor  of  Mechanical  Dentistry  in 
the  Dental  School  of  Harvard  University.  With  Illustrations.  Octavo. 
Price .         .         .51.25 

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original,  and  by  authors  writing  on  the  subject. 


LEGG  (j.  wickham),  M.  D. 

Member  of  the  Royal  College  of  PhysiclanS)  &c. 

A  GUIDE  TO   THE   EXAMINATION  OF  THE  URINE. 


For 


the  Practitioner  and  Student.  Fourth  Edition.  i6mo.  Cloth.  Price,  ^0.75 

Dr.  Legg's  little  manual  has  met  with  remarkable  success;  the  speedy  exhaustion  of  two 
editions  has  enabled  the  author  to  make  certain  emendations  which  add  greatly  to  ita  value. 
It  caa  confidently  be  commended  to  the  student  as  a  safe  and  reliable  guide. 

LEARED  (ARTHUR),  M.D.,  F.R.C.P. 

IMPERFECT  DIGESTION:  ITS  CAUSES  AND  TREATMENT. 
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KOLLMEYER  (a.  h.),  A.  M.,  M.  D. 

Professor  of  Materia  Medica  and  Therapeutics,  Montreal  College, 

CHEMIA  COARTATA  ;  or.  The  Key  to  Modern  Chemistry.    With 
Numerous  Tables,  Tests,  &c.,  &c.     Price,        ....     $2.25 

LIVEING  (EDWARD).  M.  D. 

ON    MEGRIM.    SICK-HEADACHE,    AND    SOME    ALLIED 

DISORDERS.     With  Colored  Plate.     Octavo         .         .         .     $5-25 


c 
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22 
LEWIN   (dr.  george). 

Professor  at  the  Fr.-Wllh.  Unlversltyi  and  Surgeon-ln-Chlef  of  the  Syphilitic  Wards  and  Skin  Diseases  of 

the  Charity  Hospltali  Berlin. 

THE  TREATMENT  OF  SYPHILIS  by  Subcutaneous  Sublimate 
Injections.  With  a  Lithographic  IMate  illustrating  the  Mode  and  Proper 
Place  of  administering  the  Injections,  and  of  the  Syringe  used  for  the 
purpose.     Translated  by  Carl  Prqcgler,  M.D.,  late  Surgeon  in  the 

'  Prussian  Service,  and  E.  H.  Gale,  M.D.,  late  Surgeon  in  the  United 
.   States  Army.     Price $^-5^ 

MASON  (FRANCIS),  F.  R.  C.  S., 

Surgeon  and  Lecturer  on  Anatomy  at  St.  Thomas'  Hospital,  Slc, 

THE  SURGERY  OF  THE  FACE.  With  loo  Illustrations,  En- 
graved on  Wood,  of  Various  Operations  Performed.      Octavo.     Cloth. 

Price,  $2.25 


LIZARS  (JOHN),  M.  D. 

Late  Professor  of  Surgery  in  the  Royal  College  of  Surgeons,  Edinburgh. 

THE  USE  AND  ABUSE  OF  TOBACCO.  From  the  Eighth 
Edinburgh  Edition.      i2mo.     Price,  in  flexible  cloth,  .         $o.c;o 

Tills  little  work  contains  a  History  of  the  introtluetiou  of  Tobacco,  its  penerul  characteris- 
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MACNAMARA  (c). 

Surgeon  to  the  Ophthalmic  Hospital,  and  Professor  of  Ophthalmic  Medicine  in  the  Medical  College,  Calcutta. 

MANUAL  OF  THE  DISEASES  OF  THE  EYE.  The  Third 
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Plates,  Diagrams  of  the  Eye,  many  Illustrations  on  Wood,  Snellen's 
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MARSH    (SYLVESTER). 

SECTION-CUTTING.     A  Practical  Guide  to  the  Preparation  and 

Mounting  of  Sections  for  the  Microscope  —  special  prominence  being 
given  to  the  subject  of  Animal  Sections.     With  Illustrations.     Cloth. 

Price,  $0.60 

MACKENZIE  (morell),  M.  D., 

Physician  to  the  Hospital  for  Diseases  of  the  Throat,  Jic. 

GROWTHS  IN  THE  LARYNX.  Their  History,  Causes,  Symp- 
toms, &c.  With  Reports  and  Analysis  of  One  Hundred  Cases.  With 
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OTHER    WORKS  BY  THE  SAME  AUTHOR. 

THE   LARYNGOSCOPE   IN   THROAT   DIS^-.ASES.     With  an 

Appendix  on  Rhinoscopy.     Third  Edition,  Enlarged.     With  New  Il- 
lustrations.    Price  ........ 

THE  DISEASES  OF  THE  THROAT  AND  NOSE.  Including 
The  Pharynx,  The  Larynx,  Trachea,  CEsophagus,  Nose,  Neck,  &c. 
With  numerous  Illustrations.      Preparing. 

DIPHTHERIA.     Its  Nature,  Varieties,  and  Treatment.    Price,  $07$ 

PHARMACOPCEIA  OF  THE  HOSPITAL  FOR  DISEASES  OF 
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gles, &c.,  &c.     Fourth  Edition.     Preparing. 


Skin  Diseases  of 

Sublimate 

and  Proper 

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gcoa  in  the 

the  United 

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ations,  En- 
ivo.  Cloth. 
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the    Eighth 

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23 

MEIGS  AND  PEPPER. 

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THE  PRACTICE  OF  MEDICINE 


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24 


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■  01 

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26 

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Late  Surgeon  to  the  Pcnnsylv&nla  Hospital,  Slc, 

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26 

PARKES  (EDWARD  A.),  M.  D., 

Professo.  of  Military  Hygiene  in  the  Army  Medical  Scliool,  Lc, 

A  MANUAL  OF  PRACTICAL  HYGIENii.  The  Fifth  Revised 
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POWER  (henry),  M.  B.,  F.  R  .C.  S., 

Senior  Ophthalmic  Surgeon  to  St,  Bartholomew's  Hospitali 

THE  STUDENT'S  GUIDE  TO  THE  DISEASES  OF  THE  EYE. 

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do  much  towards  elevating  the  profession  of  this  country. —  American  Journal,  of  Obstetrics. 


PAGET  (jAMEs),  F.R.S., 

Surgeon  to  St.  Bartholomew's  Hospital,  &c. 

SURGICAL  PATHOLOGY.  Lectures  delivered  at  the  Royal  Col- 
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1 


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PHYSICIAN'S  PRESCRIPTION  BOOK.  Containing  Lists  of 
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27 
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Honorary  Surgeon  to  the  Dover  Convalescent  Hotnis,  &c,,  &c. 

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28 
RINDFLEISCH  (dr.  edward). 

Professor  of  Pathological  Anatomy,  University  of  Bonn. 

TEXT-BOOK  OF  PATHOLOGICAL  HISTOLOGY.     An  Intro. 

duction  to  the  Study  of  Pathological  Anatomy.  Translated  frum  the 
German,  by  Wm.  C.  Kloman,  M.D.,  assisted  by  F.  T.  Miles,  M.D., 
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pathological  structural  changes,  and  his  book  is  consequently  well  known  to  readers  of  (ier- 
luan  medical  literature.  What  makes  it  especially  valuable  is  the  fact  that  it  was  originated, 
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Assistant  Physician  and  Teacher  of  Clinical  Medicine  in  the  University  College  Hospital  |  Assistant  Physician 

Brompton  Consumption  Hospital,  &c. 

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lecturp:s  on  the  clinical  uses  of  electricity. 

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PHILOSOPHY  OF  MARRIAGE,  in  its  Social,  Moral,  and  Physi- 
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11 


29 


An  Intro* 

=d  from  the 

ILES,  M.D., 

Containing 

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6.00 

the  subject  in 
L  forms  a  mine 
interpret  arij^ht 
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isely  illustrated, 
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\sslstant  Physician 

CTICE  OF 

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its  object  is  to 
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for  the  various 
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of  very  many 
|il  Practice,  and 
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Jones  and  Sieveking's  Pathologina!   Anatomy.     A  New  Enlarged  Edition,  edited  by  J. 
F.  Pavnk,  IM.  D.     With  Illustrations.     Price,  8550. 

■'A'^ilks  and    Moxon's    Pathological  Anatomy.    Second   Edition,   Enlarged  and   Revised. 
Price,  .{6.00. 

Carpenter's  Microscope  and    its  Revelations.     The  Fifth   Edition,  very  much    Enlarged. 
With  500  Illustrations.     Price,  85.00. 

Wilson's  Anatomist's  Vade  Mecum.     The  Ninth  Enlarged  L.indon  Edition.     Price,  85.oo. 

Parke's  Manual  of  Practical   Hygiene.       The  Fifth  Enlarged  Edition.     Price,  86.00. 

Richardson's     Mechanical     Dentistry.      Second    Edition,   much    Enlarged.     With   over   i.^o 
Illustrations.     Price,  in  cloth,  ^4.00  ;  leather,  $4.50. 

Beale's  Use  of  the  Microscope  in  Practical  Medicine.     Fourth  Edition.     500  Illustra- 
tions.    Price,  87.50 
Sweringen's   Dictionary  of  Pharmaceutical  Science.     Octavo.     Price,  83. cio. 
Mackenzie's  Growths  in  the  Larynx.     With  Numerous  Colored  Illustrations.     Price,  82.00. 
Tanner's  Index  of  Diseases,  and  their  Treatment.     .-\  New  Edition.     Price,  JI3. 00. 
Tidy's   Hand-Book  of  Modern  Ciiemistry.     Organic;  and  Inorganic.     Price,  $5.00. 
Churteris'   Hand -Book  of  Practice.     Illustrated.     Price, ;^2. 00. 


5 


i 

I 


AMERICAN  HEALTH  PRIMERS^ 

Edited  by  W.  W.  KEEN,  M.D., 

Fellow  of  the  College  Physiciana,  Philadelphia,  Surgeon  to  St.  Mary's  Hospital,  &c. 

It  is  one  of  tlie  chief  merits  of  tlie  Medical  Profession  in  modern  times  that  its  members 
are  in  tlie  fore-front  of  every  movement  to  prevent  disease.  It  is  due  to  them  that  the 
Science  of  what  has  Ijeen  liajjjjily  called  "  Preventive  Medicine  "  lias  its  existence.  Not  only 
in  larp;e  cities,  hut  in  every  town  and  hamlet,  the  Doctor  leads  in  every  effort  to  eradicate  the 
sources  of  disease.  These  efforts  have  i)een  ably  seconded  by  intelligent  and  public-spirited 
citizens  of  many  callings.  The  American  Public  Health  Association  and  the  Social  Science 
Association,  with  their  manifold  and  most  useful  influences,  are  organizations  which  have 
sprung  fiom.and  still  further  extend  and  reinforce,  the  efforts  to  improve  the  public  health. 

But  the  great  mass  of  the  public  scarcely  recognize  the  importance  of  such  efforts,  or,  if 
they  do,  are  ignorant  of  the  facts  of  Anatomy,  Physiology,  and  Hygiene,  and  of  their  prac- 
tical applicatioi.  to  the  betterment  of  their  health  and  the  prevention  of  disease.  Such 
knowledge  does  not  come  by  nature.  In  most  cases,  in  fact,  it  is  a  direct  result  of  the  most 
laborious  research  and  the  highest  skill.  Accordingly,  it  is  the  object  of  this  series  of 
American  Health  Primers  to  diffuse  as  widely  and  as  cheaply  as  jwssible,  among  all  classes, 
a  knowledge  of  the  elementary  facts  of  Preventive  Medicine,  and  the  bearings  and  appli- 
cations  of  the  latest  and  best  researches  in  every  branch  of  Medical  and  Hygienic  Science. 
They  are  not  intended  (save  incidentally)  to  assist  in  curing  disease,  but  to  teach  people 
how  to  take  care  of  themselves,  their  children,  their  pupils,  and  their  employes. 

The  series  is  written  from  the  American  standpoint,  and  with  especial  reference  to  our 
Climate,  Architecture,  Legislation,  and  modes  of  Life ;  and  in  all  these  respects  we  differ 
materially  from  other  nations.  Sanitary  I^egislation  especially,  which  in  England  has  made 
such  notable  progress,  has  barely  begun  with  us,  and  it  is  hoped  that  the  American  Health 
Primers  may  assist  in  developing  a  public  sentiment  favorable  to  proper  sanitary  laws, 
especially  in  our  large  cities. 

The  subjects  selected,  are  of  vital  and  practical  im]iortance  in  every-day  life.  They  are 
treated  in  as  popular  a  style  as  is  consistent  with  their  nature,  technical  terms  being  avoided 
as  far  as  practicable.  Eacli  volume,  if  the  subject  calls  for  it,  will  be  fully  illustrated,  so 
that  the  text  may  be  clearly  and  readily  understood  by  any  one  heretofore  entirely  ignorant 
of  the  structure  and  functions  of  the  body.  The  authors  have  been  selected  with  great 
care,  and  on  account  of  special  fitness,  each  for  his  subject,  by  reason  of  its  previous  careful 
study,  either  privately  or  as  public  teachers. 

Dr.  W.  W.  Keen  has  undertaken  the  supervision  of  the  series  as  Editor,  but  it  will  be  un- 
derstood that  he  is  not  responsible  for  the  statements  or  opinions  of  the  individual  authors. 

The  following  volumes  are  in  press,  and  will  be  issued  about  once  a  month. 


I. 


(By  CHAS.  H.  BURNETT,  M.D.,of  Philada., 

<  Si/>i;i;>ii  iiif/icDj^,'  of  riiila.  Disp.  for  Diseases  of 
(.         ///(■  Ear,  Aurist  to  Prcshyterian  liosf>ital,  etc. 

Lona  Life  and  How  to  Reach  It  JByj.  g.  RiCHARDSON,M.D.,of  Phiiada., 

l_Ony   Lim,  dnu   now   lO   nUdCn   ll.  |      rr,f.  of  Hygiene  in  University  of  Pe>tna.,  etc. 

(  By  WILLIAM  S.  FORBES,  M.D.,  of  Phila., 

\      Surgeon  to  the  l-fisco/'iit  Hospital,  etc. 

(  By  JAMES  C.  WILSON,  M.D.,  of  Philada., 

<  Li'cturer   on  Physical  Diagnosis    in    fcfferson 
(         Medical  College,  etc. 

By  GEORGE  C.  HARLAN,  M.D.,  of  Phila., 
Sii7-geon  to  tlie  II  ills  (Eye)  Hospital. 
(By  J.  SOLIS  COHEN,  M.D.,  of  Philada., 
-<      Lecturer  on  I  israses  o/  the  Throat  in  f-ferson 
(.         Medical  CoUei;e. 

(  By  HAMILTOI^  OSGOOD,  M.D.,  of  Boston, 
\     Editorial  Staff' Boston  Med.  and  Surg.  Journal. 
fByJ.  W.  WHITE,  M.D.,D.D.S.,  of  Philada., 
\      Editor  of  the  Dental  Cosmos. 


Hearing,  and  How  to  Keep  It 

II. 

III.  Sea  Air  and  Sea  Bathing. 

IV.  The  Summer  and  its  Diseases. 

V.  Eyesight,  and  How  to  Care  for  It. 

VI.  The  Throat  and  the  Voice. 

VII.  The  Winter  and  its  Dangers. 
VIII.  The  Mouth  and  the  Teeth. 
IX.  Our  Homes. 

The  Skin  in  Health  and  Disease. 


JBy  HENRY  HARTSHORNE,M.D.,  of  Phila., 

I      Formerly  Prof,  of  Hygiene  in  I'niver.  of  Penna, 


X. 
XI. 


Brain  Work  and  Overwork. 


By  L.  D.  BULKLEY,  M.D.,  of  New  York., 

Phy.fician  to  tlie  SIdn  Department  of  the  Ih-inilt 
Pi.\pensary  and  of  the  A'ew  \  'ork  J/ospital. 
(  By  H.  C.  WOOD,  Jr.,  M.D.,  of  Philada., 
-;      Clinical  J'rofessor  of  Nervous  Diseases  in  the 
y         L.tiversity  of  Pennsylvania,  etc. 

Other  volumes  are  in  preparation,  including  the  following  subjects:  "Preventable 
Diseases,"  "Accidents  and  Eme-gencies,"  "  Towns  we  Live  In,"  "Diet  in 
Health  and  Disease,"  ■  Th  Art  of  Nursing,  '  "School  and  Industrial  Hy- 
giene," "  Mental  Hygiene,"  etc.,  etc.  They  will  be  ibnio  in  size,  neatly  printed 
on  tinted  paper,  and  bound  in  cloth,  50  cents. 

Mailed  Iree  upon  receipt  of  price. 

LINDSAY  &  BLAKISTON,  Publishers,  Pliihulelphia. 


pital,  &c. 

at  its  members 
them  that  the 
ice.  Not  only 
)  eradicate  the 
public-spirited 
Social  Science 
ns  which  have 
puhlic  health. 
1  efforts,  or,  if 

of  their  prac- 
lisease.  Such 
lit  of  the  most 
this  series  of 
ing  all  classes, 
igs  and  appli- 
;ienic  Science. 

teach  people 
yts. 

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)ects  we  differ 
land  has  made 
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sanitary  laws, 

fe.  They  are 
being  avoided 
illustrated,  so 
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:ed  with  great 
evious  careful 

t  it  will  be  un- 
idiial  authors. 


j.,'of  Philada., 

''.for  Diseases  of 
an  Hospital,  etc. 
,  of  Philada., 
o/  Penaa.,  etc. 
.D.,of  Phila., 
a/,  etc. 

,  of  Philada., 
is    in    JcJ/'erson 

D.,of  Phila., 

bital. 

"  Philada., 

■oat  in  J'-'O'erson 

D.,  of  Boston, 

i  Siir^.  yournal. 
S.,  of  Philada., 

i/I.D.,of  Phila., 

iiiver.  of  Penna. 
"New  York., 
/.•/  ()/  tlic  Dcniilt 
'oik  Uos/>ital. 

Philada., 

Diseases  in  the 
•tc. 

'reventable 
,"  "Diet  in 
ustrial  Hy- 

ncatly  printed 
oth,  50  cents. 


iilelphia. 


